It was narrated from alHasan concerning Sa"d, the freed slave of Abu Bakr, who used to serve the Prophet (ﷺ) ,that

the Prophet (ﷺ) liked his service and said: "O Abu Bakr, manumit Saʼd." He said: O Messenger of Allah, we have no helper except him. The Messenger of Allah (ﷺ) said: “Manumit Sa’d; other men are coming, other men are coming.” Abu Dawood said: i.e., slaves.