Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to say, "Someone who breaks the fast in Ramadan because he is ill or travelling should make up the days he has missed consecutively."
Muwatta Malik Book 18, Hadith 50
← Previous Hadith Yahya related to me from Malik from Zayd ibn Aslam from his brother Khalid ibn Aslam that Umar ibn al-Khattab once broke thefast on a cloudy day thinking that evening had come and the sun had set. Then a man came to him and said, "Amir al-muminin, the sun has come out,'' and Umar said, "That's an easy matter. It was our deduction (ijtihad)."

Malik said, "According to what we think, and Allah knows best, what he was referring to when he said, 'That's an easy matter' was making up the fast, and how slight the effort involved was and how easy it was. He was saying (in effect), 'We will fast another day in its place.' "

Muwatta Malik Book 18, Hadith 49 Next Hadith → Yahya related to me from Malik from Ibr Shihab that Abdullah ibn Abbas and Abu Hurayra differed about making up days missed in Ramadan. One of them said that they were done separately and the other said that they were done consecutively. He did not know which one of them it was who said that they were done separately.

Muwatta Malik Book 18, Hadith 51