is it haram to not accept money when someone giving money?
If the money is halal then it is considered a gift so it is allowed.
There no harm to not take it. However it is recommended to take it.
Humility is one of the best and noblest of characteristics; it is the attitude of the Prophets and Messengers, and the way of the close friends of Allaah and the righteous. That is being kind to people, lowering the wing of humility to them and trying to meet their needs and wants.
It was narrated from Abu Sa’eed al-Khudri (may Allaah be pleased with him) that the Messenger of Allaah (peace and blessings of Allaah be upon him) said:
“The most perfect of the believers in faith is the one who is best in attitude and humble, who get along with others and others get along with them, and there is no good in the one who does not get along with others and they do not get along with him.”
Narrated by al-Tabaraani in al-Awsat (2/268); classed as hasan by al-Albaani in al-Silsilah al-Saheehah (751).
One of the greatest qualities of those who are humble is that they accept gifts no matter what their value, and they do not look at their value or whether the giver could have afforded something better than that, rather one should accept it and appreciate it, and feel that the true gift is the love that motivated them to give, not the value of the gift.
The leader of mankind, the Seal of the Prophets and Messengers, our Beloved Muhammad (peace and blessings of Allaah be upon him), despite his high status and lofty position, would accept a gift even if it was a sheep’s foot or a drink of milk.
It was narrated from Abu Hurayrah that the Prophet (peace and blessings of Allaah be upon him) said:
“If I were invited to a meal of a sheep’s foot I would accept, and if I were given a sheep’s foot as a gift, I would accept.”