Praise be to Allah.
Whoever has intercourse with his wife during the day in Ramadaan has sinned and must offer expiation, which is to free a slave. If that is not possible then he must fast for two consecutive months. If he cannot fast, then he must feed sixty poor persons. It is not permissible for him to feed poor persons if he is able to fast.
The evidence that it is obligatory to offer expiation for having intercourse during the day in Ramadaan is the report narrated by al-Bukhaari (1963) from Abu Hurayrah (may Allaah be pleased with him) who said: “Whilst we were sitting with the Prophet (peace and blessings of Allaah be upon him), a man came to him and said: ‘O Messenger of Allaah, I am doomed!’ He said, ‘What happened to you?’ He said: ‘I had intercourse with my wife whilst I was fasting.’ The Messenger of Allaah (peace and blessings of Allaah be upon him) asked: ‘Could you find a slave you could set free?’ He said, ‘No.’ He asked, ‘Are you able to fast for two consecutive months?’ He said, ‘No.’ He asked, ‘Can you feed sixty poor persons?’…”
This hadeeth indicates that the fast of two months must be consecutive, because the Prophet (peace and blessings of Allaah be upon him) said: “Are you able to fast for two consecutive months?”
If a person begins to fast, then Ramadaan comes, he should fast Ramadaan, then break his fast for Eid, then complete the fast of two months, and not start fasting again from the beginning, because the Ramadaan fast does not affect the continuity of his fast.
Ibn Qudaamah (may Allaah have mercy on him) said: If a person begins to fast in expiation for zihaar [a jaahili and haraam form of divorce] at the beginning of Sha’baan, he should break his fast on the day of [Eid] al-Fitr and then carry on. The same applies to one who begins [such a fast] at the beginning of Dhu’l-Hijjah; he should break his fast on the Day of Sacrifice [Eid al-Adha] and the days of al-Tashreeq, and then continue on the basis of his previous fasts.
To sum up: If the fast in expiation for zihaar is interrupted by a day on which his expiatory fast is not valid, such as if he begins fasting at the beginning of Sha’baan then is interrupted by Ramadaan and the day of al-Fitr, or he begins in Dhu’l-Hijjah then is interrupted by the day of sacrifice and the days of al-Tashreeq, then the continuity is not affected by that, and he should carry on from where he left off, on the basis of the fasts he has already completed. End quote from al-Mughni (8/29).
It is not essential to feed the sixty poor persons in one go; rather he may feed one group, then feed another group, at different times, until he has fed sixty. For more information please see the answer to question no. 1672.
And Allaah knows best.