What are the things that are excused due to forgetfulness and the things that are not excused by it?

Question : May Allah be your guide and your protector. The questioner says: Forgetfulness is a legal excuse for the Muslim, but how is the distinction made between the legal rulings that are made up due to forgetfulness and those that are excused by the excuse?

Answer : This is known by the well-known rule among scholars that obligatory acts are not excused by forgetfulness, while prohibited acts are excused by forgetfulness. This is the rule: a person is excused for prohibited acts due to forgetfulness and ignorance, but not for obligatory acts. This is the criterion. The evidence for this is the man who came and prayed a prayer in which he did not settle (in the positions). What did the Messenger (peace and blessings be upon him) say to him? He said: "Pray again, for you have not prayed." His ignorance did not benefit him because he left an obligatory act, which is settling (in the positions).
And the man who spoke while he was praying, being ignorant. What did the Messenger (peace and blessings be upon him) say to him? Did he say to him: "Repeat the prayer," or did he say: "In this prayer, nothing of the speech of people is valid," and did not order him to repeat it?
The second is the man who spoke when the Prophet (peace and blessings be upon him) had finished his prayer. He said to him: "In this prayer, nothing of the speech of people is valid," and did not order him to repeat it. Why?
Because he was ignorant and had committed a prohibited act, which is speaking in prayer. So this is the rule followed by scholars: what is from the category of obligatory acts is not excused by ignorance and forgetfulness, and what is from the category of prohibited acts is excused by ignorance.