It is related in an athar in al-Daarimi  on the authority of ‘Amr ibn Salamah who said:
We were sitting at the door of ‘Abd-Allah ibn Mas’ood before Fajr prayer, so that if he came out, we could walk with him to the Masjid,, then Abu Moosa al-Ash’ari came to us and said: Has Abu ‘Abd al-Rahmaan come out to you yet? We said: No. So he sat with us until he came out, and when he came out we all stood up. Abu Moosa said to him: O Abu ‘Abd al-Rahmaan, just now I saw something in the mosque that I have never seen before, but I do not think it was anything but good. He said: What was it? He said: If you live, you will see it. He said: In the mosque I saw some people sitting in circles waiting for the prayer. In every circle there was a man, and in their hands they had pebbles. He would say: Say Allahu akbar (Allah is Most Great) one hundred times, and they would say Allahu akbar one hundred times. He would say: Say Laa ilaaha ill-Allah (there is no god but Allah) one hundred times, and they would say Laa ilaaha ill-Allah one hundred times. He would say: Say Subhaan-Allah (Glory be to Allah) one hundred times, and they would say Subhaan-Allah one hundred times. He said: What did you say to them? He said: I did not say anything to them; I was waiting to see what you think and I waited for your command. He said: Why did you not tell them to count their bad deeds and guarantee to them that their good deeds would not be wasted? Then he moved on and we moved on with him until he came to one of those circles, and he stood over them and said: What is this that I see you doing? They said: O Abu ‘Abd al-Rahmaan, these are stones with which we count the takbeers (‘Allahu akbar’), tahleel (‘Laa ilaaha illa-Allah’) and tasbeeh (‘Subhaan-Allah’). He said: Count your bad deeds, for I guarantee to you that none of your good deeds will be lost. Woe to you, O ummah of Muhammad! How quickly you have become doomed! His companions are still alive and his cloak has not worn out, and his vessel is not yet broken. By the One in Whose hand is my soul, you are either following a way that is more guided than the way of Muhammad or you are opening the door to misguidance. They said: By Allah, O Abu ‘Abd al-Rahmaan, we intended nothing but good. He said: How many of those who intended good did not achieve it? The Messenger of Allah (sallallaahu ‘alaihi wa sallam) told us that some people would recite the Qur’an and it would not go any further than their collarbones. By Allah, I do not know, perhaps most of them are from among you. Then he turned away from them and ‘Amr ibn Salamah said: We saw most of the people of those circles fighting alongside the Khawaarij against us in the battle of Nahrawaan.
The above report clearly shows without a doubt that the companions of the Prophet (sallallaahu ‘alaihi wa sallam) used to not tolerate any type of unknown practice related to the shar’iah. Rather, they were strict in assuring that they performed all acts of shari’ah exactly as the Prophet taught them without any deviation. And it must be taken into account that Ibn Mas’ood had been with the Prophet for a long time since the days of Mecca, hence, he understood limits of the Shari’ah very well and it is not possible that this direct criticism was just an opinion of his as some people claim. In fact, he was one of the earliest Muslims to accept Islam in Mecca. The above report is a common account cited by numerous reputable scholars in warning people against bid’ah (religious innovation). For example, Ibn al-Jawzee said in his famous Talbees Iblees slightly before mentioning a similar report from Ibn Mas’ood that, “Even an invented practice which did not contradict the Shari’ah or imply any change was disliked by the majority of early scholars. They used to avoid any innovation, even though certain types were allowable, in order to protect the basic principle of adherence (Ittibaa’).” Religious innovations are defined as “those things which are newly introduced [in the religion] having no source in the Shari’ah proving them” and “in most cases, innovations conflict with divine law by implying a need for human additions or deletions.” Usually people’s intention with such additions or deletions is to draw near to Allah; however, Allah will not accept such types of innovations from its doers because they have no basis in the shari’ah. This is why the Prophet said, “Whoever introduces into this affair of ours that which is not of it, then it is rejected.” And the Messenger of Allah also used to say often in his Friday sermons that, “The worst affairs are the newly invented matters [in religion] and every newly invented matter is misguidance and every misguidance is in the fire.” However, as for those practices that have a basis in the Shari’ah and do not contradict it, then they are permissible though they may be innovations from a linguistic point of view as pointed out by Ibn al-Jawzee, al-Uthaymeen, Ibn Taymiyyah, and Ibn Rajab al-Hanbali. Imam As-Shafa’I said:
“There are two types of newly introduced matters: that which is introduced which is contrary to the Book and the Sunnah, or to a tradition [from someone among the right-acting first generations] or something on which there is consensus, then this innovation is an error. That which is newly introduced of good actions and which does not contradict any of the above, then this newly introduced matter is not blameworthy.”
Examples of this include Umar uniting people under one imam in Ramadan for prayer, compilation of the Qur’an in one book, writing down the explanations of hadiths and of the Qur’an, etc.
We also learn from the above report that it is in our best interest to stick to the understanding of the early generations, specifically the companions. They witnessed the revelation of Allah (subhaanahoo wa ta’aala) and the actions of the Prophet Muhammad before their very eyes, hence; they understood and knew the religion better than anyone else after them. And the Prophet Muhammad affirmed this when he said:
“My nation will splinter into seventy-three sects, all of which will be in the fire except one.” When the [companions] asked “Which sect is it, O Messenger of Allah?” He replied, “The one followed by my companions and myself.”
And the Messenger of Allah is also reported to have said, “I have been sent [as an Apostle] in the best of all the generations of Adam’s offspring since their creation.” Imam al-Barbahaaree said, “The foundation upon which the Jama’ah is built is the companions of the Prophet…They are Ahl us-Sunnah wal-Jamaa’ah, so whoever does not take from them has gone astray and innovated.” Imam al-Awzaa’ee said, “Knowledge is what comes from the companions of Muhammad and that which does not come from a single one of them is not knowledge.” The first three generations of Islam, in particular, are blessed and are superior to the later generations as pointed out by the Messenger of Allah himself when he stated, “The best people are those living in my generation, then those coming after them, and then those coming after [the second generation].” Therefore, their interpretation of the religion is to be given preference over the later generations because their hearts were the most sincere and their religious understanding the most pure due to the short time frame between them and the Messenger of Allah. The later generations were inflicted with influences from other philosophies and ideologies, which came into them as a result of Islam spreading throughout the world and Muslims coming into contact with such foreign ideas. Hence, the great scholars of the early generations and those who followed them strongly advised their students to stick to the teachings of the early generations as Imam Al-Awzaa’ee once said, “Take the path of your righteous predecessors for verily what was sufficient for them is sufficient for you.”
There is also a stern warning in this report against those who collectively engage in group dhikr with one voice. Ibn Mas’ood was not aware of any such practice to take place during their time with the Prophet, hence, he warned them against it. In essence, it is highly recommended to praise and glorify Allah with our tongues. However, it is the method in which they were praising and glorifying Allah that bothered Ibn Mas’ood. This is just like the one who wants to pray five units of Isha prayer instead of the established four or the one who wants to make three prostrations in the prayer instead of the established two. If the person who did such an act were to respond, “I only intend to do good and what is wrong with worshipping Allah with five units or adding an extra prostration in the prayer,” it would never be accepted from him even though in essence praying and doing prostrations are good actions. This is because the method of worship is just as important as the worship itself and both of them need to be in accordance to the practice of the Messenger of Allah. The Prophet Muhammad did not just teach us what types of worships to do but also how to do them. Shaykh al-‘Uthaymeen said, “Whoever does an action-even if it has an origin in the legislation, but it is done in a fashion that was not ordered-then it is rejected.” And the general principle, when it comes to worship, is that every type of worship is forbidden except that which is based on evidence. A good display of this understanding is shown by one of the top students of the companions, Sa’id bin Al-Musayyib:
Sa’id bin Al-Musayyib – Allah have mercy on him – once saw a man praying more than two units after the beginning of Fajr, making many bows and prostrations, and so he forbade him. The man said, “O Abu Muhammad, is Allah going to punish me for praying?” Sa’id said, “No, but He will punish you for contradicting the Sunnah.”
Some of the people of knowledge also derived from this report the prohibition on the use of a rosary during dhikr. They are considered a form of innovation by some scholars such as Shaykh al-Albaanee and Shaykh Bakr Abu Zayd, but are considered permissible by others such as Ibn Taymiyyah, al-‘Uthyameen and many others due to additional reports that show some basis for it from the actions of the companions. Hence, al-‘Uthyameen concluded:
“It is better not to do tasbeeh with the rosary, but it is not an innovation, because there is a basis for it, which is the fact that some of the companions did tasbeeh with pebbles. But the Messenger taught that tasbeeh with the fingers is better.”
Lastly, we learn from the above report that the Qur’an is not just there to be recited, but also to be understood. The Qur’an was sent so that it may be implemented into the lives of the believers and followed. As Allah Says (the meaning of which is) in the Qur’an [16:89], “And We have sent down to you the Book as clarification for all things and as guidance and mercy and good tidings for the Muslims.” Therefore, the Qur’an is a guide throughout the believer’s life which clarifies for him the right course to take and warns him against misguidance and disobedience against his Creator. And this guide can only be implemented if its reader understands it. It is interesting to note that Ibn Mas’ood quoted the Prophet Muhammad to state that the Qur’an “would not go any further than their collarbones.” The meaning here is that it would not reach their hearts. It is well known that the mind and heart are connected and they both communicate with the other. Allah in the Qur’an connected the ability to reason with the heart, for example, when He said (the meaning of which is) [22:46], “So have they not traveled through the earth and have hearts by which to reason?” This is why Shaykh al-‘Uthaymeen said:
“There is no doubt that the heart is the place for the intellect, but the brain is the function of thinking. Once the brain produces the thought, it prepares it and sends it to the heart. Then, the heart commands it or prohibits it. It’s like the brain is the secretary that prepares things then sends them to the heart. After they reach the heart, it either commands or prohibits these things.”
Similarly, Allah said (the meaning of which is) [6:25], “And among them are those who listen to you [when you recite], but We have placed over their hearts coverings, lest they understand it.” Allah here explicitly concludes that the Qur’an reaching the heart is a means to its understanding. And the opposite of it is also true that if it does not reach the heart, then a person will not understand it. Such people do not understand the religion of Allah or His book even though they may recite it. And it was these very same people who later joined the Khawaarij and were visited by Ibn Abbas before the battle of Nahrawaan, in which they were defeated, where he said to them:
“Tell me what you have against Allah’s Messenger’s son-in-law [i.e. Ali], the Emigrants, and the Helpers among whom the Qur’an was revealed? There is not a single one of them among you and they know the Qur’an’s interpretation better than you.”
Therefore, the Muslim must always assure that he not only recites the Qur’an as a way of lip service but also that he understands the true meaning behind it in order that he may implement Allah’s commandments and keep away from His prohibitions.
 Reported by ad-Daarimee (210) and others, and graded authentic by al-Haithamee (Al-Majma`, 1/181, 189), al-Haitamee (Az-Zawaajir, al-Kabeerah #51), al-Albaanee (As-Saheehah, 2005; Ar-Radd `alal-Habashee, p.45-47), `Abd-ul-Muhsin al-`Abbaad (Al-Hathth `alat-tibaa`-is-Sunnah, p.49), Bakr Aboo Zaid (Tas-heeh-ud-Du`aa’, pp.149, 153 & 154), Husayn Asad (Musnad-ud-Daarimee, 210), Mashhoor Salmaan (Al-Amr bil-Ittibaa`, pp.83-84), `Umar Aboo Bakr (Al-Mataalib-ul-`Aaliyah, 12/518-519/2983) and others, as cited by hadeeth.webs.com/authentic/sunnah/mawqifsalaf.html.
 Reported by an-Nasa’ee (3/188) and it is declared saheeh by Shaikh al-Albaanee in Saheeh Sunan in-Nasaa’ee (no. 1487), as cited in the footnotes of Explanation of the Creed by Barbahaaree (pg. 25)
 Al-Bayhaqi As-Sunan Al-Kubraa 2:466. Shaykh Al-Albaanee graded it sahih in Irwa Al-Ghalil 2:236, as cited by http://www.islamport.com
 Al-Silsilat al-Da’eefah (1/110), as cited by http://www.islamqa.com/en/ref/3009
 Al-Fataawa (22/187), as cited by http://www.islamqa.com/en/ref/3009
 Al-Liqa’ al-Maftooh (3/30), as cited by http://www.islamqa.com/en/ref/3009
 al-‘Uthaymeen’s explanation of Riyadh us-Saliheen (2/ 212-214), as cited by http://abuaaliyah.multiply.com/journal/item/205/Is-the-Intellect-in-the-Brain-or-the-Heart-
Ansari, Muhammad ‘Abdul-Haqq. Ibn Taymiyyah Expounds on Islam. Riyadh: Imam Muhammad Ibn Saud University, 2000.
Al-Barbahaaree, Abu Muhammad al-Hasan ibn ‘Alee. Explanation of the Creed. Trans. Abu Talhah Daawood ibn Ronald Burbank. Birmingham: Al-Haneef Publications, 1995.
al-Jawzee, Abdur-Rahmaan ibn ‘Alee ibn Ja’far. The Devil’s Deception. Trans. Dr. Abu Ameenah Bilal Philips. Birmingham: Al-Hidaayah Publishing and Distribution, 1996.
Rajab al-Hanbali, ‘Abd ar-Rahman ibn Ahmad ibn ‘Abd ar-Rahman (Rajab). The Compendium of Knowledge and Wisdom. Trans. Abdassamad Clarke. London: Turath Publishing, 2007.
Taimiyah, Ahmed ibn Abdul Haleem ibn Abdussalam. The Right Way: A Summarized Translation. Trans. n.t. Riyadh: Darussalam, 1996.
al-‘Uthaymeen, Muhammad Ibn Saaleh. Bid’ah and Their Evil Effects. Trans. Aboo ‘Abd-illaah as-Sayalaanee. Birmingham: Salafi Publications, 1999.
—. Explanatory Notes on Imaam an-Nawawee’s Forty Ahadeeth (Revisited). 2nd Edition. Trans. Aboo Mu’aawiyah ‘Aqeel ibn Kenneth Ingram. Dallas: Tarbiyyah Publishing, 2008.