"It is made lawful for you to have sexual relation with your wives on the night of As-Saum (the fasts) ... (till) ... and seek that which Allah has ordained for you (offspring).. ." (V.2:187)

Sahih al-Bukhari · Book 65 · Hadith 4508

حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ إِسْرَائِيلَ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْبَرَاءِ، وَحَدَّثَنَا أَحْمَدُ بْنُ عُثْمَانَ، حَدَّثَنَا شُرَيْحُ بْنُ مَسْلَمَةَ، قَالَ حَدَّثَنِي إِبْرَاهِيمُ بْنُ يُوسُفَ، عَنْ أَبِيهِ، عَنْ أَبِي إِسْحَاقَ، قَالَ سَمِعْتُ الْبَرَاءَ ـ رضى الله عنه ـ‏.‏ لَمَّا نَزَلَ صَوْمُ رَمَضَانَ كَانُوا لاَ يَقْرَبُونَ النِّسَاءَ رَمَضَ…

Narrated Al-Bara': When the order of compulsory fasting of Ramadan was revealed, the people did not have sexual relations with their wives for the whole month of Ramadan, but some men cheated themselves (by violating th…