Mawlā (Arabic: مَوْلَى‎, plural mawālī (مَوَالِي)), is a polysemous Arabic word, whose meaning varied in different periods and contexts.[1]

In the days before Muhammad, the term originally applied to any form of tribal association.[2]

In the Quran and hadiths it is used in a number of senses, including 'Lord', 'guardian', 'trustee', and 'helper'.

After Muhammad's death, this institution was adapted by the Umayyad dynasty to incorporate new converts to Islam into Arab-Muslim society and the word mawali gained currency as an appellation for converted non-Arab Muslims in the early Islamic caliphates.

https://en.wikipedia.org/wiki/Mawla
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http://muslimscholars.info/manage.php?submit=Find&yfield=3&s...
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Right n. 27: The Right of the Freed Slave

حق المولى الجارية عليه نعمتك

https://www.al-islam.org/divine-perspective-rights/right-n-2...
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https://forum.wordreference.com/threads/مولى.1827428/
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If طاوس بن كيسان represents one of the mawali (موالي) then, I imagine, it would be the first translation, i.e. freed man / salve / servantor even client . In fact, there was once the Kaysaniyyah movement which comprised such individuals, i.e. the mawali موالي. This is not to say that this person (طاوس بن كيسان) belonged to it. Just that he may be connected in some way (e.g. by decent) to those who were part of this movement.

https://forum.wordreference.com/threads/مولى.1827428/
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والله أعلم