Mukhtasar Muslim (Abridged) 906 — Slave’s reward for loyalty

Narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings of Allah be upon him) said: Indeed, when a slave is sincere to his master and worships Allah well, then he will have a double or twofold reward (compared to a free person).