What is the ruling on the prayer of an imam who stood up immediately after the first prostration in the first rak'ah and remained standing, then said "Allahu Akbar" and prostrated after being prompted by the congregants, and completed his prayer and performed two prostrations of forgetfulness, considering that the imam performed the sitting between the two prostrations while he was standing?

Sitting between the two prostrations and maintaining tranquility therein is a pillar of prayer according to the majority of scholars, and the prayer is not valid without them. Abu Hanifa and Malik differed, saying: Tranquility and sitting are not obligatory; rather, it is sufficient to merely lift the head from the ground. The evidence for the majority is the Prophet's (peace be upon him) saying: "Then raise yourself until you are calmly sitting."

Based on this, regarding the prayer of an Imam who did not sit between the two prostrations, there are two opinions among the Malikis:

1. Al-Khurashi's opinion: The prayer is invalid because sitting between the two prostrations is an obligation. 2. Al-Adawi's opinion: The apparent view is that it is valid, considering what Ashhab narrated, that one who omits a prostration should prostrate immediately from standing without sitting.

However, the more cautious approach and the one that absolves the Imam's responsibility is for him to repeat the prayer, thereby avoiding the disagreement.