Is zakat obligatory on the orphans' money that has reached the nisab, or should it be left for them to pay it themselves when they grow up?

Zakat is obligatory on orphans' money immediately upon reaching the nisab and the passing of a complete lunar year. It is not permissible to delay it until they grow up, because Zakat is immediately obligatory when its payment is possible, based on the Almighty's saying: "And give its due on the day of its harvest." Also, delaying it might lead to its forfeiture due to the death of the owner or the destruction of the wealth, which harms the poor. Furthermore, it is an act of worship that recurs, so it is not permissible to delay it.