Is it permissible to switch to the expiation for fasting (fasting three days a week) instead of fulfilling a recurring vow to pray 20 rak'ahs and recite three parts of the Qur'an, due to the difficulty of fulfilling the vow and the accumulation of expiations?

A person should not resort to vows, even if the intention is to compel oneself to obedience or to abandon sin. Rather, one must possess a strong resolve to forsake sin and repent from it. If the vow is made with the intention of drawing closer to Allah after falling into sin, then it is obligatory to fulfill it. However, if the vow is to restrain and deter oneself from sin without the intention of seeking closeness to Allah, then an expiation for a broken oath (kaffarat yameen) is required. Some scholars, in this case, offer the choice between an expiation for a broken oath and fulfilling the vowed action. If the time for fulfilling the vowed action has passed, then an expiation for a broken oath is required.