Narrated Umm Salamah, Ummul Mu'minin: Safinah said: I was a slave of Umm Salamah, and she said: I shall emancipate you, but I stipulate that you must serve the Messenger of Allah (ﷺ) as long as you live. I said: Even if you do not make a stipulation, I shall not leave the Messenger of Allah (ﷺ). She then emancipated me and made the stipulation with me

English translation · Sunan Abu Dawud