What is the fast that is made up on behalf of the deceased?

The Shaykh : Because the well-known position in the school of thought is that only the fast of a vow is made up on behalf of the deceased, do you understand? And the saying of the Messenger of Allah (peace and blessings be upon him), as narrated by 'A'ishah, which is authentic: This is regarding a vow, but there is no evidence for restricting it to that. And, glory be to Allah, how can the hadith be restricted to a vow when the occurrence of a vow is rare?
And fasting in Ramadan occurs frequently. How many people die before making up their Ramadan fasts? And how few are those who have a vow upon them that is made up for them? Restricting the hadith to a rare matter when there is a matter that is far more common is not correct. So the correct view is that it is made up for him, but not on the basis of obligation. Because if we said it is obligatory for the guardian to fast, that would imply that he is sinful for leaving it.
And Allah the Exalted said: So we feed on his behalf if the rich man says, "I will not fast." We say, "Feed," if he has no estate, because he feeds from his estate. If he has no estate, we say that if someone volunteers to feed on his behalf, he is to be thanked and rewarded. And if no one does it, it is dropped from him, because he did not find anything. Yes.