Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 847
Sahl b. Sa'd al-Sa'idi reported: The Apostle of Allah (may peace be upon him) went to Bani Amr b. 'Auf in order to bring about reconciliation amongst them. The rest of the hadith is the same but with (the addition of these words):" The Messenger of Allah (may peace be upon him) came and made his way through the rows till he came to the first row and Abu Bakr retraced his steps."