It was narrated that Anas bin Malik said:
"What the Messenger of Allah (ﷺ) most enjoined when he was dying and breathing his last was: The prayer; and those whom your right hands possess." (FR)
English reference (FR): Vol. 3, Book 22, Hadith 2697 (FR)
Arabic reference (FR): Book 22, Hadith 2801 (FR)