The slave should not say Rabbi or Rabbati (My lord, My lady)
حَدَّثَنَا ابْنُ السَّرْحِ، أَخْبَرَنَا ابْنُ وَهْبٍ، قَالَ أَخْبَرَنِي عَمْرُو بْنُ الْحَارِثِ، أَنَّ أَبَا يُونُسَ، حَدَّثَهُ عَنْ أَبِي هُرَيْرَةَ، فِي هَذَا الْخَبَرِ وَلَمْ يَذْكُرِ النَّبِيَّ صلى الله عليه وسلم قَالَ " وَلْيَقُلْ سَيِّدِي وَمَوْلاَىَ " .
The tradition mentioned above has also been transmitted by Abu Hurairah through a different chain of narrators. This version does not mention the Prophet (May peace be upon him) i.e, it does not go back to him. It has : He must say: “My master” (sayyidi) and “My patron” (mawlaya).