when a slave acts sincerely towards his master and worship Allah well, he will have a double reward. (Using translation from Abū Dāʾūd 5169)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ إِذَا نَصَحَ الْعَبْدُ لِسَيِّدِهِ وَأَحْسَنَ عِبَادَةَ رَبِّهِ كَانَ لَهُ مِنَ الْأَجْرِ مَرَّتَيْنِ