Is it permissible to give charity from money if a mother made her son swear not to give it as charity, and is that considered disobedience?

Obligatory charity, such as zakat (definition), must be given, and it is not permissible to obey one's mother in preventing it. It is obligatory to give it, and if it can be done without her knowledge, that is preferable. As for non-obligatory charity, if a mother prevents her son from giving it, her obedience becomes obligatory, because obedience to parents is obligatory while charity is supererogatory, and the obligatory takes precedence over the supererogatory. However, if the mother's prevention of supererogatory charity is mere foolishness and has no valid purpose, then her obedience is not obligatory.