Surat Al-Ahzaab (The Clans) - الأحزاب

لَّا يَحِلُّ لَكَ ٱلنِّسَآءُ مِنۢ بَعْدُ وَلَآ أَن تَبَدَّلَ بِهِنَّ مِنْ أَزْوَٰجٍ وَلَوْ أَعْجَبَكَ حُسْنُهُنَّ إِلَّا مَا مَلَكَتْ يَمِينُكَ وَكَانَ ٱللَّهُ عَلَىٰ كُلِّ شَىْءٍ رَّقِيبًا ﴿٥٢﴾

It is not allowed to you to take women afterwards, nor that you should change them for other wives, though their beauty be pleasing to you, except what your right hand possesses and Allah is Watchful over all things.