Amr bin al-Harith bin Ya'qub عمرو بن الحارث · Fasting (Kitab Al-Siyam)

Al Bara’ (bin Azib) said “When a man fasted and slept, he could not eat till (another nigh) like it.” Sarmah bin Qais Al Ansari came to his wife while he was fasting and asked her Do you have something (to eat)? She replied “No”. Let me go and seek something for you. So, she went out and sleep overcame him. She came (back) and said (to him) .You are deprived (of food). He fainted before noon. He used to…

A man came to the Prophet (ﷺ). He broke his fast during Ramadan. He then narrated the rest of this tradition adding: Then a huge basket containing fifteen sa's of dates was brought to him. He said: Eat it yourself and your family and keep one fast and beg pardon of Allah.

If I had some part of the fast of Ramadan to make up, I would not be able to atone for it except in Sha'ban.