And those who preserve their chastity Save with their wives and those whom their right hands possess (i.e. slave girls), for thus they are not blameworthy [Quran 70:29]
First of all, what you have in the brackets in not part of the original, and the term “what your right hand possess” could apply to both male as well as female slaves. The word used in the Quran is ‘ma malakat amanu-kum’ which is an euphemism for a prisoner of war, male or female, who had become a slave. The proof of this can be found in the other verses of the Quran:
1. [30:28] He does propound to you a similitude from your own (experience): do ye have partners among those whom your right hands possess, to share as equals in the wealth We have bestowed on you? Do ye fear them as ye fear each other? Thus do we explain the Signs in detail to a people that understand.”
Here, obviously, the same term “whom your right hand possess” is used in a non-gender epithet for slaves. Why would Quran say that about women slaves but not about male ones?
2. [33:55] There is no blame (on these ladies if they appear) before their fathers or their sons, their brothers, or their brother’s sons, or their sisters’ sons, or their women, or the (slaves) whom their right hands possess. And, (ladies), fear God; for God is Witness to all things.”
Here the entire verse is addressed to women and again the same term is used to describe male slaves owned by a woman. “Their women” include a woman’s female servants or slaves.
3. [16:71] God has bestowed His gifts of sustenance more freely on some of you than on others: those more favored are not going to throw back their gifts to those whom their right hands possess, so as to be equal in that respect. Will they then deny the favors of God?
Again, the term “whom your right hand possess” is used as a non-gender description of a slave.