Sayyiduna Ibn Umar (may Allah be pleased with him) narrated from the Messenger of Allah (peace and blessings be upon him): "The slave who is sincere towards his master and worships Allah in an excellent manner has a double reward."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15807
Sayyiduna Abu Musa (may Allah be pleased with him) narrated from the Prophet (peace and blessings be upon him): "The slave who worships Allah in an excellent manner, fulfils the rights of his master, and obeys him and is sincere towards him, has a double reward: one for the worship of Allah, and the other for obeying his master and fulfilling his right."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15808
Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "The righteous and sincere slave has a double reward." By the One in whose hand is the soul of Abu Hurayrah, were it not for jihad in the path of Allah, Hajj, and kindness to my mother, I would have loved to die while still a slave.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15809
Abu Hurayrah (may Allah be pleased with him) narrated this saying of the Messenger of Allah (peace and blessings be upon him): "When a slave fulfils the right of Allah and the right of his masters, he receives a double reward." He said: I narrated this hadith to Ka'b (may Allah have mercy on him), and he said: There is no reckoning upon him, nor upon an abstinent believer of little means.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15810
Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Glad tidings to the slave who dies in a state of worshipping Allah and fully fulfilling the rights of his master; glad tidings to him, glad tidings to him."
In one narration al-Ramadi added these words: Whenever Umar (may Allah be pleased with him) passed by a slave, he would say: "O so-and-so, glad tidings to you of a double reward."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15811