Sahih al-Bukhari — Fighting for the Cause of Allah (Jihaad) — Hadith No: 2888
Translation
Narrated Anas:I was in the company of Jabir bin `Abdullah on a journey and he used to serve me though he was older than I. Jarir said, "I saw the Ansar doing a thing (i.e. showing great reverence to the Prophet (ﷺ) ) for which I have vowed that whenever I meet any of them, I will serve him