Ibn ‘Umar (may Allah be pleased with him) reported: The Messenger of Allah (may Allah’s peace and blessings be upon him) said: 'If a slave serves his master sincerely and worships Allah properly, he will have a double reward.'" Abu Mūsa al-Ash‘ari (may Allah be pleased with him) reported: The Messenger of Allah (may Allah’s peace and blessings be upon him) said: "A slave who worships his Lord properly and discharges his duties towards his master, and is sincere and obedient to him will get a double reward." Authentic hadith - Al-Bukhari and Muslim with its two versions