Is deducting a monthly sum from one's salary for the poor—in fulfillment of a vow made after obtaining a job and parental approval of it—considered charity for the sake of Allah, or is it merely the fulfillment of a vow for which one is only rewarded for the act of fulfillment itself?

Allah Almighty praised those who fulfill their vows, and the Prophet, peace and blessings be upon him, condemned those who make vows but do not fulfill them, because fulfilling a vow is an emphasized obligation. Voluntary charity cannot have a greater reward than it, and the Prophet, peace and blessings be upon him, said: "My servant does not draw near to Me with anything more beloved to Me than what I have enjoined upon him."