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. (Using translation from Muslim 2249b)   

قَالَ رَسُولُ اللهِ ﷺ لَا يَقُولَنَّ أَحَدُكُمْ عَبْدِي فَإنَّ كُلَّكُمْ عَبْدٌ وَلَكِنْ لِيَقُلْ فَتَايَ وَلَا يَقُلْ أَحَدُكُمْ مَوْلَايَ فَإِنَّ مَوْلَاكُمُ اللهُ وَلَكِنْ لِيَقُلْ سَيِّدِي  

The Prophet ﷺ said: None of you must say: "My slave" (abdi) and "My slave-woman" (amati), and a slave must not say: "My lord" (rabbi or rabbati). The master (of a slave) should say: "My young man" (fataya) and "My young woman" (fatati), and a slave should say "My master" (sayyidi) and "My mistress" (sayyidati), for you are all (Allah's slave and the Lord is Allah, Most High. (Using translation from Abū Dāʾūd 4975)   

أَنَّ رَسُولَ اللهِ ﷺ قَالَ لَا يَقُولَنَّ أَحَدُكُمْ عَبْدِي وَأَمَتِي وَلَا يَقُلِ الْمَمْلُوكُ رَبِّي وَرَبَّتِي وَلَكِنْ لِيَقُلِ الْمَالِكُ فَتَايَ وَفَتَاتِي وَالْمَمْلُوكُ سَيِّدِي وَسَيِّدَتِي فَإِنَّكُمُ الْمَمْلُوكُونَ وَالرَّبُّ اللهُ سُبْحَانَهُ وَتَعَالَى