Is an expiatory offering (kaffara) required for someone who vowed to memorize the entire Qur’an but was unable to fulfill their vow?

A vow must be fulfilled if its condition is met, based on the Almighty’s saying: "And let them fulfill their vows," and the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him."

If you are unable to fulfill the vow due to an incapacity that is not expected to cease, such as despairing of memorizing the Quran, then the expiation for a broken oath (kaffarat yamin) is obligatory, based on the Prophet, peace and blessings be upon him, saying: "And whoever vows a vow he cannot fulfill, its expiation is the expiation for a broken oath."