Is zakat obligatory on saved money that currently has no source of income, part of which was received as aid from a sister?

If the money you have saved and what your sister gave you reaches the nisab (definition), which is approximately equivalent to 85 grams of pure gold or 595 grams of pure silver, and a full lunar year (hawl) has passed on it, then zakat (definition) becomes obligatory upon you. Zakat does not decrease wealth; rather, it increases it, makes it grow, and blesses it. Allah replaces for the one who gives charity many times what they spent, as Allah Almighty says: "And whatever thing you spend [in His cause] - He will compensate it; and He is the best of providers."