It is narrated from al-Hasan (may Allah have mercy on him) that Sayyiduna Abu Bakrah (may Allah be pleased with him) entered the mosque while the Prophet (peace and blessings be upon him) had already gone into bowing. He too bowed before joining the row. The Prophet (peace and blessings be upon him) said (after the prayer): "May Allah Almighty increase your eagerness (for prayer). Do not do it like this again."
Imam al-Shafi'i (may Allah have mercy on him) said: His (peace and blessings be upon him) words 'Do not do it again' are like his saying 'Do not come to the prayer running.' That is: it is not required of you to bow until you reach your place in the row, because there is hardship in that, just as it is not required of you to run when you hear the iqamah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2584
Hadith Gradingمحدثین:صحيح
Hadith Takhrij«صحيح۔ امام بخاريa ني موسيٰ بن اسماعيل عن همام روايت كي هي۔ اخرجه مالك في الموطا 285»
It is narrated from Abu Bakr bin Abd al-Rahman that Sayyiduna Abu Bakr al-Siddiq and Sayyiduna Zayd bin Thabit (may Allah be pleased with them both) entered the mosque while the imam was bowing. They both bowed at once, then, while still in the state of bowing, they walked until they joined the row.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2585
It is narrated from Ibn Shihab (may Allah have mercy on him): Abu Umamah bin Sahl bin Hunayf (may Allah be pleased with him) informed me that he saw Zayd bin Thabit (may Allah be pleased with him) enter the mosque while the imam was bowing. He walked on until it became possible for him to reach the row while bowing, then he said the takbir and went into bowing, then, while bowing, he walked slowly until he joined the row.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2586
It is narrated from Zayd bin Wahb: I went out with Abdullah bin Mas'ud (may Allah be pleased with him) from his house towards the mosque. When we reached the middle of the mosque, the imam bowed. Abdullah (may Allah be pleased with him) said the takbir and bowed, and I bowed with him. Then we walked in the state of bowing until we reached the row just as the people raised their heads. When the imam completed the prayer and said the salam, I stood up, because I thought that I had not caught the rak'ah. Abdullah bin Mas'ud (may Allah be pleased with him) took hold of my hand and sat me down, then said: You have caught the rak'ah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2587