Sahih al-Bukhari 6082
Sahih al-Bukhari · Book 78: Good Manners and Form (Al-Adab) · The establishment of a bond of brotherhood and the conclusion of a treaty
Narrated Anas:
حَدَّثَنَا مُسَدَّدٌ ، حَدَّثَنَا يَحْيَى ، عَنْ حُمَيْدٍ ، عَنْ أَنَسٍ ، قَالَ لَمَّا قَدِمَ عَلَيْنَا عَبْدُ الرَّحْمَنِ فَآخَى النَّبِيُّ صلى الله عليه وسلم بَيْنَهُ وَبَيْنَ سَعْدِ بْنِ الرَّبِيعِ فَقَالَ النَّبِيُّ صلى الله عليه وسلم " أَوْلِمْ وَلَوْ بِشَاةٍ " .
When `Abdur-Rahman came to us, the Prophet (ﷺ) established a bond of brotherhood between him and Sa`d bin Ar-Rabi`. Once the Prophet (ﷺ) said, "As you (O `Abdur-Rahman) have married, give a wedding banquet even if with one sheep."