Sahih al-Bukhari 4508
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · "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)
Narrated Al-Bara':
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 رَمَضَانَ كُلَّهُ، وَكَانَ رِجَالٌ يَخُونُونَ أَنْفُسَهُمْ، فَأَنْزَلَ اللَّهُ {عَلِمَ اللَّهُ أَنَّكُمْ كُنْتُمْ تَخْتَانُونَ أَنْفُسَكُمْ فَتَابَ عَلَيْكُمْ وَعَفَا عَنْكُمْ} .
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 that restriction). So Allah revealed: "Allah is aware that you were deceiving yourselves but He accepted your repentance and forgave you.." (3.187)