Is it permissible for a father to prevent his son from proposing to a girl, claiming inability to marry, even though the son is confident in his ability to marry after a period, and the girl is of good character and religious commitment?

Filial piety is among the most emphasized duties, and the Lord's pleasure is in the parents' pleasure. If you desire a religious girl and your father is refusing, then exert your effort in convincing him by mentioning her religious merits and by enlisting the help of relatives. If your father rejects this specific girl but accepts another, then it is not permissible for you to disobey him, because obedience to him is obligatory, while marrying this girl is not. And whoever gives up something for the sake of Allah, Allah will compensate him with something better. However, if your father rejects your marriage altogether, and you are capable of it and fear temptations, then you are not obliged to obey him in this case, and you may marry, while striving to be kind to him. Perhaps his refusal stems from a fear that marriage might affect your academic achievements.