The Prophet ﷺ said, "How excellent it is for one of them to worship his Lord well and to be sincere to his master."In another wording, "How excellent it is for a slave to die while worshipping Allah well and serving his master faithfully. How excellent it is for him."
قال النبي ﷺ: نعم ما لأحدهم يحسن عبادة ربه و ينصح لسيده وفي لفظ: نعما للمملوك أن يتوفى يحسن عبادة الله، وصحابة سيده، نعما له.
Bukhari narrated it in the Book of Manumission (2549) via Amash, who said, Abu Salih narrated to us, from Abu Hurairah, and he mentioned it.Muslim narrated it in the Book of Oaths and Vows (2667:46) via Maamar, from Hammam bin Munabbih, from Abu Hurairah, and he mentioned it with the second wording.