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.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ يَقُولَنَّ أَحَدُكُمْ عَبْدِي وَأَمَتِي وَلاَ يَقُولَنَّ الْمَمْلُوكُ رَبِّي وَرَبَّتِي وَلْيَقُلِ الْمَالِكُ فَتَاىَ وَفَتَاتِي وَلْيَقُلِ الْمَمْلُوكُ سَيِّدِي وَسَيِّدَتِي فَإِنَّكُمُ الْمَمْلُوكُونَ وَالرَّبُّ اللَّهُ ﷻ  

He must say: “My master” (sayyidi) and “My patron” (mawlaya).  

عَنْ أَبِي هُرَيْرَةَ فِي هَذَا الْخَبَرِ وَلَمْ يَذْكُرِ النَّبِيَّ ﷺ قَالَ وَلْيَقُلْ سَيِّدِي وَمَوْلاَىَ  

The Prophet ﷺ said: Do not call a hypocrite sayyid (master), for if he is a sayyid, you will displease your Lord, Most High.  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ تَقُولُوا لِلْمُنَافِقِ سَيِّدٌ فَإِنَّهُ إِنْ يَكُ سَيِّدًا فَقَدْ أَسْخَطْتُمْ رَبَّكُمْ ﷻ