Sahih Muslim 1111 a
The Book of Fasting
The strict prohibition of intercourse during the day in Ramadan for one who is fasting; And the obligation of offering major expiation and the definition thereof; And that it is obligatory for both the one who can afford it and the one who cannot afford it, and it remains an obligation for the one who cannot afford it until he has the means
Abu Huraira (Allah be pleased with him) reported that a person came to the Messenger of Allah (ﷺ) and said: Messenger of Allah, I am undone. He (the Prophet) said: What has brought about your ruin? He said: I have had intercourse with my wife during the month of Ramadan. Upon this he (the Holy prophet) said: Can you find a slave to set him free? He said: NO He (the Prophet (ﷺ) again) said: Can you observe fast for two consecutive months? He said: No. He (the Prophet) said: Can you provide food to sixty poor people?, He said: No. He then sat down and (in the meanwhile) there was brought to the Messenger of Allah (ﷺ) a basket which contained dates. He (the Prophet) said: Give these (dates) in charity. He (the man) said: Am I to give to one who is poorer than I? There is no family poorer than mine between the two lava plains of Medina. The Messenger of Allah (ﷺ) laughed so that his molar teeth became visible and said: Go and give it to your family to eat.