The Messenger of Allah ﷺ said, "When a slave is sincere toward his master and worships his Lord well, he receives a double reward."
حدثنا محمد بن عبيد حدثنا عبيد الله عن نافع
أن رسول الله ﷺ قال إذا نصح العبد لسيده وأحسن عبادة ربه كان له من الأجر مرتين
Its isnad is sahih, and it has already appeared as no. 4673 from Yahya and Muhammad bin Ubayd, from Ubaydullah, and it has already appeared as no. 4706 from Yahya alone, from Ubaydullah, see also no. 4799.