Sahih Muslim
The Book Concerning the Use of Correct Words (Kitab Al-Alfaz min Al-Adab wa Ghairiha)
Book Number: 027 / Hadith Number: 5592
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: None of you should say: My bondman, for all of you are the bondmen of Allah, but say: My young man, and the servant should not say: My Lord, but should say: My chief.