Surah Al-Mu'minun 23:6

إِلَّا عَلَىٰٓ أَزْوَٰجِهِمْ أَوْ مَا مَلَكَتْ أَيْمَـٰنُهُمْ فَإِنَّهُمْ غَيْرُ مَلُومِينَ

Except from their wives or those their right hands possess, for indeed, they will not be blamed -

Translation: Saheeh International

Tafsir

except from their spouses that is to their spouses and what slaves their right hands possess that is concubines for then they are not blameworthy in having sexual intercourse with them.

Excerpt from Tafsir al-Jalalayn, commentary on 23:6, via Quran.com. The reader has the full commentary and 9 more tafsirs.