Is inferring that something is an innovation because the Companions did not do it, such as celebrating the Mawlid or congratulating on Friday, considered an innovation?

Bid'ah (innovation) is anything introduced into the religion without proof. The Companions and scholars inferred that a specific act was a bid'ah based on the Prophet (peace be upon him) and his Companions abandoning it, despite the presence of a motive to perform it. This is because the religion has reached perfection, and the Companions were the first to embrace every good deed. Therefore, anything they did not do, despite the existence of a reason for it, is considered a bid'ah.

This is supported by the incident of Ibn Mas'ud with those who were collectively remembering Allah using pebbles in the mosque, where he condemned their action, stating that they had innovated something that the Prophet (peace be upon him) and his Companions did not do.

This principle is further supported by Al-Shatibi's statement that the Lawgiver's silence on something, despite the presence of a reason for it, is evidence that it is a bid'ah. Similarly, Ibn Taymiyyah stated that the Prophet's (peace be upon him) abandonment of an act, despite the existence of its motive and the removal of any impediment, is a Sunnah, and adding to it is a bid'ah. Similar views were expressed by Ibn Hajar Al-Haytami, Al-Shawkani, and Al-Jizani, who affirmed that every act of worship abandoned by the righteous predecessors, despite the presence of a motive and the absence of an impediment, is a bid'ah.

Accordingly, celebrating the Mawlid (Prophet's birthday) and congratulating on Fridays (if done out of commitment and belief in their desirability) are considered bid'ahs, because the Prophet (peace be upon him) and his Companions did not do them. However, if the congratulation is casual or a prayer to greet a brother without commitment or belief in its desirability, then there is no harm in it.