Sahih Muslim Book 6, Hadith Number 2461.

Chapter : Sexual Intercourse is completely forbidden during the day in the month of Ramadhan.

Humaid b. ‘Abd al-Rahman reported that Abu Huraira had narrated to him that the Apostle of Allah (may peace be upon him) commanded the person (who) broke the fast in Ramadan to free a slave or observe fasts for two (consecutive) months or feed sixty poor persons.