Sura 33 Al-Ahzab (Those who took up arms), ayah 52

1. لَا يَحِلُّ لَكَ النِّسَاءُ مِنْ بَعْدُ وَلَا أَنْ تَبَدَّلَ بِهِنَّ مِنْ أَزْوَاجٍ وَلَوْ أَعْجَبَكَ حُسْنُهُنَّ إِلَّا مَا مَلَكَتْ يَمِينُكَ ۗ وَكَانَ اللَّهُ عَلَىٰ كُلِّ شَيْءٍ رَقِيبًا

   Not lawful to you, (O Muhammad), are (any additional) women after (this), nor (is it) for you to exchange them for (other) wives, even if their beauty were to please you, except what your right hand possesses. And ever is Allah, over all things, an Observer.

   33:52

Translation: Saheeh International