Surah An-Nisa 4:21

وَكَيْفَ تَأْخُذُونَهُۥ وَقَدْ أَفْضَىٰ بَعْضُكُمْ إِلَىٰ بَعْضٍ وَأَخَذْنَ مِنكُم مِّيثَـٰقًا غَلِيظًا

And how could you take it while you have gone in unto each other and they have taken from you a solemn covenant?

Translation: Saheeh International

Tafsir

How shall you take it that is by what right when each of you has been privily with the other through sexual intercourse which validates the dowry and they have taken from you a solemn covenant a binding pledge and that is what God commanded namely that they should be retained honourably or set free virtuously.

Excerpt from Tafsir al-Jalalayn, commentary on 4:21, via Quran.com. The reader has the full commentary and 9 more tafsirs.