Riyad as-Salihin

Anas bin Malik (May Allah be pleased with him) reported: I set out along with Jarir bin 'Abdullah Al-Bajali (May Allah be pleased with him) on a journey and he served me. I said to him: "Don't do that." Thereupon, he said, "I have seen the Ansar doing this with Messenger of Allah (ﷺ), and I swore by Allah, whenever I accompany anyone of the Ansar, I would serve him".

[Al-Bukhari and Muslim].