Being late to the imam in bowing before completing the recitation of al-Fatihah

Question:
Or does a person respond when he hears the imam reciting in the bowing position so that he can complete the recitation of al-Fatihah, given that the imam recited a short surah and did not recite it again after rising from the bowing? Is the prayer of this person valid? And what is obligatory upon him?

Answer:
This is a mistake. It is obligatory for him to bow with the imam even if he has not completed al-Fatihah. The one who arrived while the Prophet (peace and blessings be upon him) was bowing, bowed with the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) did not order him to make up that rak'ah, even though he had not recited al-Fatihah. So he follows the imam and bows with him, even if he has not recited al-Fatihah, or even if he has not completed it. This person who was late to the imam is excused due to ignorance; his prayer is valid, if Allah wills, because he was ignorant of the ruling. But he should not return to doing such a thing.