صحيح ابن خزيمه
Sahih Ibn Khuzaymah
جماع أبواب قيام المأمومين خلف الإمام وما فيه من السننChapters on Followers Standing Behind the Imam
(101) بَابُ النَّهْيِ عَنْ مُبَادَرَةِ الْإِمَامِ الْمَأْمُومَ بِالرُّكُوعِ،101| Prohibition of the imam preceding the follower in bowing
Hadith Q1594
وَالْإِخْبَارِ بِأَنَّ الْإِمَامَ مَا سَبَقَ الْمَأْمُومَ مِنَ الرُّكُوعِ، أَدْرَكَهُ الْمَأْمُومُ بَعْدَ رَفْعِ الْإِمَامِ رَأْسَهُ مِنَ الرُّكُوعِ
And the explanation of the matter that when the follower precedes the imam in going into bowing (ruku‘), the follower will make up for that precedence after the imam raises his head. (That is, the amount of his bowing will become equal to the amount of the imam’s bowing.)
