Sahih Bukhari: Hadith 2458

The Prophet (ﷺ) 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 etc.) (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).