Alhamdulillah. One: Sheikh Uthaymeen (RA) has issued a fatwa on the day which people call "birthday celebration". He said: All the festivals which are repeated every week or every year which are accepted by the people but which are not allowed in the Shariah are bidat. The proof of this is that the Shariat-maker has given the provision of observing Akika for the newborn. He didn't keep anything after that. Repeating these festivals means that people are likening these festivals to Islamic Eid. It is forbidden ; Not allowed. There is no other Eid in Islam except the three Eids permitted by Shariah: Eid-ul-Fitr , Eid-ul-Azha and the weekly Eid or Friday. This is not a class issue ; As it rotates repeatedly. For this reason, when the Prophet (peace be upon him) came to Medina, he saw the Ansar celebrating two special days. Then he said: " Surely Allah has given you two days instead of these two days: Eid- ul - Azha and Eid-ul- Fitr . " .) But this was their customary subject. [Compiled from Sharhu Kitabit Tawheed (1/362)] Do not allow this action. Islam forbids this. Since Islam does not allow it, it is not possible for you to engage in such activities. You should also tell him that if it had the permission of Allah, you would have been happy and grateful to Him. But the decision in this matter is not in my hands and not in the hands of any other person. Rather, it is God who decides. As Muslims, it is our duty to submit to God's decision, and since it is the decision of the All-Knowing and All-Wise God, it is not permissible for us to discuss or criticize it. Tell him these words in a very beautiful language and gently. If he is satisfied with it and respects your decision ; Alhamdulillah. Otherwise try to stay out of the house during this festival. So that no one can force you to join the event or you will not be mentally weak. If your mother observes it, you will have no sin. The pleasure of Allah is above the satisfaction of all creatures. You know for sure that even if your mother reverses your decision today , God will please your mother in the future ; God willing.