Does a person become an unbeliever if they vow upon themselves disbelief if they marry, or use their money, or commit something forbidden, and their vow was made boastfully of disbelief, then they repent and return to God, and then they do what they vowed?

If a person apostatizes from Islam and then repents, let him praise Allah for guiding him and rejoice in His bounty. It is permissible for him to use his wealth, for his vow made while in a state of disbelief is, according to the majority of scholars, null and void. This is because Islam is a condition for the validity of a vow, and because the act of a disbeliever is not considered an act of devotion. And if a Muslim vows to commit disbelief or a sin, he is not obligated to fulfill it by consensus, and it is not valid, and no expiation is required for it according to the majority of scholars, though it is commendable to offer an expiation for an oath.