Must one fulfill a vow to give charity on behalf of a young man who was the cause of a sin, or is refraining from doing so permissible?

Praise be to Allah for your repentance, and we ask Allah to accept it from you, to keep you steadfast upon it, and to transform your bad deeds into good ones.

You must fulfill your promise to this man and give charity on his behalf, secretly, in fulfillment of your promise, while resolving never to speak to him again, as he is not required to know about it.

Allah has praised those who give charity and fulfill their covenants and promises, and giving charity on behalf of a living person is permissible, and the one who gives charity on behalf of another also receives reward.