The Messenger of Allah ﷺ said, "When a slave is sincere to his master and worships Allah well, he receives his reward twice."
أن رسول الله ﷺ قال: العبد إذا نصح لسيده، وأحسن عبادة الله فله أجره مرتين.
Malik narrated it in "Seeking Permission" (43) from Nafi, from Abdullah bin Umar, as mentioned. Bukhari narrated it in "Manumission" (2546), and Muslim in "Oaths and Vows" (1664:43), by way of Malik, in the same manner.