Why do scholars frequently state that such-and-such an act was not known during the time of the Messenger of Allah, peace and blessings be upon him, nor his Companions, or that if there had been any good in it, they would not have abandoned it, despite the evidence that indicates the permissibility of ijtihad in everything that is good, even if there is no specific evidence for it from the Qur’an and Sunnah, and it is sufficient for it to have a basis as long as it does not contradict Islamic law?

The answer regarding the definition of innovation (bid‘ah) requires elaboration. The esteemed questioner is advised to consult the book "Qawa'id Ma'rifat al-Bida'" (Principles of Understanding Innovations) by Dr. Muhammad al-Jizani, in which he mentioned more than twenty principles on this topic. Among these principles are:

- If the Prophet, peace and blessings be upon him, abandoned an act of worship despite the presence of a motivating factor and the absence of any impediment, then performing it is an innovation. - Every act of worship that the righteous predecessors abandoned, while there was a motivating factor for it and no impediment prevented it, then performing it is an innovation. - Every act of worship that was mentioned in the Sacred Law with a specific restricted form, then changing this form is an innovation. - Every absolute act of worship established in the Sacred Law by a general proof, then restricting it to a specific time or place in a way that suggests it is legally intended without evidence is an innovation.

It is also recommended to consult the book "Al-Radd 'ala al-Luma'" by Professor Shahatah Saqr, and some related fatwas.