(11) باب ثَوَابِ الْعَبْدِ وَأَجْرِهِ إِذَا نَصَحَ لِسَيِّدِهِ وَأَحْسَنَ عِبَادَةَ اللَّهِ
Abu Huraira reported Allah's Messenger (ﷺ) as saying:
When a slave fulfils obligation of Allah and obligation of his master, he has two rewards for him. I narrated this to Ka'b, and Ka'b said: (Such a slave) has no accountability, nor has a poor believer.
Reference: Sahih Muslim 1666 a
In-book reference: Book 27, Hadith 70
USC-MSA web (English) reference(deprecated numbering scheme): Book 15, Hadith 4100