The ruling on whoever removes some of his Hair due to Ignorance after assuming Ihram

Question :

A man assumed Ihram for 'Umrah and after that he remembered that he must shave the hair of his armpits. So, he shaved it after assuming Ihram and then he set out for 'Umrah. We would like a clarification of the ruling, and you will receive the reward and blessing for that.

Answer:

Shaving the hair of the armpit is not obligatory for the Ihram, nor is plucking it. It is only recommended to pluck it or remove it with something from those clean things that remove hair before assuming Ihram. Likewise, it is recommended to trim the moustache, clip the nails and shave the pubic hair if each of these things is in need of that. It is not necessary for this to be when assuming Ihram. Rather, if the person does that before assuming Ihram while he is in his house or on the way (to Makkah), that is sufficient. There is no sin on the person whom you mentioned for shaving his armpit due to him being ignorant of the Islamic ruling. Similar to this, if the Muhrim did something from what he has mentioned forgetfully after assuming Ihram, there is no sin on him. This is due to Allâh's Statement:
"Our Lord do not take us to account (i.e., punish us) if we forget or unintentionally err."

This is also due to what is confirmed from the Prophet that indeed Allâh has answered this supplication.

Source:
Ash-Shaykh Ibn Baz
Fatawa Islamiyah, Vol. 4 Pages 137-138