It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: None of you should say regarding his slave, "Abdi" (my slave), because you are all slaves; rather, he should say, "My young man." And none of you should say regarding his master, "My Rabb" (my lord), because your Lord is Allah; rather, he should say, "My chief, my master."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10436