Should a married young man go to Hajj if he won the lottery, or should he let his father go in his place? Which is more befitting: performing the pillar or honoring one's parents?

Hajj is obligatory immediately for whoever is able to undertake it, and it is not permissible to prioritize others for obligatory acts of worship. Therefore, it is not permissible to prioritize the father over the son in performing the Hajj obligation if the son has not yet performed it, because Hajj is one of the pillars of Islam, and the son must perform his obligation first. If you contravene this and prioritize your father, and he goes for Hajj, his Hajj is valid, and you must hasten to perform Hajj when you are able. Filial piety can be achieved through other means, and sending parents for Hajj before the son performs Hajj is permissible, but the son must first perform Hajj for himself.