Sahih al-Bukhari 93
Sahih al-Bukhari · Book 3: Knowledge · Whoever knelt down before the Imam or a (religious) preacher
Narrated Anas bin Malik:
حَدَّثَنَا أَبُو الْيَمَانِ ، قَالَ أَخْبَرَنَا شُعَيْبٌ ، عَنِ الزُّهْرِيِّ ، قَالَ أَخْبَرَنِي أَنَسُ بْنُ مَالِكٍ ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم خَرَجَ، فَقَامَ عَبْدُ اللَّهِ بْنُ حُذَافَةَ فَقَالَ مَنْ أَبِي فَقَالَ " أَبُوكَ حُذَافَةُ ". ثُمَّ أَكْثَرَ أَنْ يَقُولَ " سَلُونِي ". فَبَرَكَ عُمَرُ عَلَى رُكْبَتَيْهِ فَقَالَ رَضِينَا بِاللَّهِ رَبًّا، وَبِالإِسْلاَمِ دِينًا، وَبِمُحَمَّدٍ صلى الله عليه وسلم نَبِيًّا ، فَسَكَتَ .
One day Allah's Messenger (ﷺ) came out (before the people) and `Abdullah bin Hudhafa stood up and asked (him) "Who is my father?" The Prophet (ﷺ) replied, "Your father is Hudhafa." The Prophet (ﷺ) told them repeatedly (in anger) to ask him anything they liked. `Umar knelt down before the Prophet (ﷺ) and said thrice, "We accept Allah as (our) Lord and Islam as (our) religion and Muhammad as (our) Prophet." After that the Prophet (ﷺ) became silent.