Thus did the Prophet ﷺ elucidate the matter: he prostrated at this verse while inside the prayer. Whenever one of his actions proceeds either in obedience to a divine command or as a clarification of something ambiguous, that action carries the same legal weight as his verbal instruction. This indicates that the prostration he performed upon reciting this sūrah is obligatory—especially when he is in ṣalāh. Prayer itself is obligatory, and completing it is likewise obligatory; it may not be broken off except for an act that is superior to finishing it. From this we learn that performing sujūd al-tilāwah within the prayer is better than completing the prayer without it. Were a worshipper to add, deliberately, any act of the same genus to the prayer, his prayer would be nullified—yet here the prostration of recitation is expressly prescribed.

There are two reports from Imām Aḥmad regarding whether this prostration during the prayer is mandatory; the more convincing view is that it is indeed obligatory, as we have already shown for several reasons. One of them is that the very imams themselves are commanded to “pray as you have seen me pray,” and this is precisely how the Prophet ﷺ prayed. Allah knows best.