Is the son obligated to pay his father a percentage of his monthly salary, given that the son knows his father is financially capable and does not need this money, and that this would delay the son's marriage and formation of his own family?

According to the Hanafis, Malikis, and Shafi'is, a father may take from his son's wealth whatever he wishes and possess it, but only to the extent of his need. As for the Hanbalis, he may take whatever he wishes under two conditions: that he does not unduly diminish his son's wealth or harm him, or take something the son needs, and that he does not give it to another child. If the father's request would unduly diminish the son's wealth, the son is not obligated to obey him in that specific matter. However, he must still be dutiful and kind to his father to the best of his ability, and respectfully apologize for what he cannot fulfill. Righteousness towards parents is among the best acts of devotion. The Messenger of Allah, peace and blessings be upon him, said: "The father is the middle gate of Paradise, so if you wish, you may neglect this gate or preserve it."