Ibn ‘Abbās and Abū Hurayrah – Allāh be pleased with them – said, “There is no harm in making up [fasts of] Ramaḍān separately from one another.”
ʿAbd Al-Razzāq, Al-Muṣannaf 4:243; Ibn Abī Shaybah, Al-Muṣannaf article 9114; Al-Dāraquṭnī, Al-Sunan 2:193.
Abū ‘Ubaydah b. Al-Jarrāḥ – Allāh be pleased with him – said, when asked about making up missed fasts of Ramaḍān separately, “Allāh did not legislate upon you the breaking of the fast, and then cause hardship on you when making it up, so count the days [you excusably missed] and fast them as you wish.”
Ibn Abī Shaybah, op. cit. article 9133.
Anas b. Mālik – Allāh be pleased with him – said, “If you wish, make up [missed fasts of] Ramaḍān consecutively, or if you wish, make them up separately.”
Ibid. article 9115.