Is Zakat obligatory on the remaining money that a father gave for study and living expenses if a Hawl (lunar year) passes over it, knowing that it may not be enough to complete the study and the student will need more?

If the remaining money reaches the nisab (threshold) and a full year has passed over it, then zakat becomes obligatory, even if it is intended for expenses or study fees. This is due to the generality of the evidence regarding the obligation of zakat when its conditions are met. The nisab is equivalent to 85 grams of gold or 595 grams of silver. The amount to be given is 2.5%, along with the blessings and growth the zakat payer receives, for Allah Almighty says: (Take, [O Muhammad], from their wealth a charity by which you purify them and cause them increase, and invoke [Allah's blessings] upon them. Indeed, your invocations are reassurance for them. And Allah is Hearing and Knowing) and for the Prophet, peace and blessings be upon him, saying: (Charity does not decrease wealth).