Sahih Bukhari, Chapter: Manumission of Slaves

The Prophet (SAW) said, "You should not say, 'Feed your lord (Rabbaka), help your lord in performing ablution, or give water to your lord' but should say, 'my master (e.g. Feed your master instead of lord) (Saiyidi)', or my guardian (Maulai), and one should not say, my slave (Abdi), or my girl-slave (Amati), but should say, my lad (Fatai), my lass (Fatati), and 'my boy (Ghulami).' "