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. (Using translation from Abū Dāʾūd 3932)  

أَنْ تَخْدُمَ النَّبِيَّ ﷺ مَا عِشْتَ فَقُلْتُ إِنْ لَمْ تَشْتَرِطِي عَلَيَّ مَا فَارَقْتُ النَّبِيَّ ﷺ مَا عِشْتُ فَأَعْتَقَتْنِي وَاشْتَرَطَتْ عَلَيَّ  

“Umm Salamah freed me but stipulated that I should serve the Prophet ﷺ as long he lived.” (Using translation from Ibn Mājah 2526)  

أَنْ أَخْدُمَ النَّبِيَّ ﷺ مَا عَاشَ»