Is it permissible for sisters to pay their Zakat to their poor, needy sister for an expensive medication, knowing that she has saved money that she cannot access at the moment, and is Zakat obligatory on that saved money?

A woman whose income is insufficient to cover her basic needs, and who cannot access her absent wealth, is eligible for Zakat. Her sisters are permitted to give her Zakat from their own wealth; in fact, she takes precedence over other eligible recipients due to her kinship.

If the impediment is removed and she gains access to her wealth, then if it is sufficient for her basic needs, she is considered wealthy and is not eligible for Zakat. Otherwise, she remains eligible.

Regarding paying Zakat on absent wealth that meets the conditions for Zakat, there is a difference of opinion among scholars. The minimum threshold (nisab) is the equivalent of 85 grams of gold or 595 grams of silver.