Is it permissible to give the zakat on gold saved for three years to a sick sister?

If the purpose of acquiring gold is for permissible use, then zakat is not obligatory on it. However, if it is for trade, hoarding, or prepared as a dowry for a future wife, then zakat is obligatory on it, provided its net weight reaches 85 grams and a full year has passed while it is at this threshold. The amount of zakat is a quarter of a tenth (2.5%), and it is obligatory for past years.