What is meant by a worshiper not listening to the Imam, and is there a specific measure for it? Does the ruling differ if it was done intentionally, and what is the ruling on the prayer of one who did not listen to the Surah recited by the Imam?

Scholars have differed regarding humility (khushu') in prayer. The majority opinion is that it is recommended, not obligatory. Therefore, the prayer of one who did not listen to the imam's recitation due to heedlessness and lack of attentiveness is valid, and he is not required to repeat it, as long as he fulfilled its pillars and obligations. However, one should strive for humility and attentiveness in prayer, for it is its essence, its spirit, and its greatest objective.