Whoever enters the Masjid (mosque) while the Imam is in the bowing position then bows like him before he rises, catches the Rak`ah (unit of prayer). The basic evidence for this is the Hadith of
Abu Bakrah Al-Thaqafy (may Allah be pleased with him) who entered the Masjid and found the Prophet (peace be upon him) in the bowing position, then he bowed before reaching the row. When this was mentioned to the Prophet (peace be upon him), he said to him, "May Allah increase your love for good, but do not repeat it again (bowing in that way).
Related by Imam
This Hadith is clear evidence that catching a Rak`ah without recitation of Surah Al-Fatihah is considered one Rak`ah because Allah's Messenger (peace be upon him) (Part No. 7; Page No. 318) did not order him to make up for it even though
Abu Bakrah (may Allah be pleased with him) did not recite Al-Fatihah. Had this been a specific case to Abu Bakrah, the Prophet (peace be upon him) would have mentioned this. The legal texts are essentially of general application. This is the opinion of the Four Imams (Imams Abu Hanifah, Malik, Al-Shafi`y, and Ahmad) and the majority of religious scholars.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.