Must a son hand over his entire salary or a portion of it to his father, especially after the father financed the son's education and there was no prior agreement on that?

Firstly, the father is obligated to provide for his children's education until they reach maturity and are capable of earning a living. According to the Hanbalis, he is obligated to provide for them even after maturity if they are poor and not actually employed. However, the majority of jurists believe that this obligation does not extend beyond maturity.

Secondly, if the son works and earns money, he is not obligated to give it to his parents unless they are in need of financial support. In such a case, he is obligated to spend on them according to their needs, not his entire earnings. A father may take from his children's money if he is in need, provided that it does not harm them, and that he does not take from one to give to another. The son is advised to show kindness and dutifulness to his parents and to give them from his money what does not harm him.