He spoke about the narrations of Hudhayfah and Ibn Mas'ud regarding the condemnation of religious innovations.

The Shaykh : But among the Salafi narrations that are not well-known is what is reported from Hudhayfah ibn al-Yaman (may Allah be pleased with him), who said: "Any act of worship that the Companions of the Messenger of Allah (peace and blessings be upon him) did not perform, do not perform it." So, do not perform it. And in this vein is the saying of 'Abdullah ibn Mas'ud: "Moderation in the Sunnah is better than exertion in a religious innovation," "Moderation in the Sunnah is better than exertion in a religious innovation," and similar to his other saying: "Follow and do not innovate, for you have been sufficed with the ancient matter." You have been sufficed with the ancient matter.
In response to these narrations, the answer to that question is that if a latecomer enters the mosque and finds that the imam has finished praying, has said the closing salam, and there are others who have already joined late, we say: It is not permissible for this latecomer to follow any of those latecomers. Why? For two reasons. The first is the great principle mentioned earlier: any act of worship that the Messenger of Allah (peace and blessings be upon him) did not perform, do not perform it. The second reason is that something similar to this has occurred, although it is different.