Surah Al-Baqarah, ayah 222

وَيَسۡـَٔلُونَكَ عَنِ ٱلۡمَحِيضِۖ قُلۡ هُوَ أَذٗى فَٱعۡتَزِلُواْ ٱلنِّسَآءَ فِي ٱلۡمَحِيضِ وَلَا تَقۡرَبُوهُنَّ حَتَّىٰ يَطۡهُرۡنَۖ فَإِذَا تَطَهَّرۡنَ فَأۡتُوهُنَّ مِنۡ حَيۡثُ أَمَرَكُمُ ٱللَّهُۚ إِنَّ ٱللَّهَ يُحِبُّ ٱلتَّوَّٰبِينَ وَيُحِبُّ ٱلۡمُتَطَهِّرِينَ ٢٢٢

Wayas'alūnaka 'anil-mahīdi qul huwa adhan fa'tazilun-nisā'a fil-mahīdi walā taqrabūhunna hattā yathurna fa idhā tatahharna fa tūhunna min haythu amarakumullāhu innallāha yuhibbut-tawwābīna wayuhibbul-mutatahhirīn

And they ask you about menstruation. Say, "It is harm, so keep away from wives⁸² during menstruation. And do not approach them until they are pure. And when they have purified themselves,⁸³ then come to them from where Allāh has ordained for you. Indeed, Allāh loves those who are constantly repentant and loves those who purify themselves."