It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her); she said: At the time of his death, most of the final counsel of the Messenger of Allah (peace and blessings be upon him) was: "Take care of the prayer, and take care of those whom your right hands possess."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19994