What are the consequences for my mother, who vowed to take her older brother for Hajj—when he was young—if her brother is unable to perform the pilgrimage with her this year due to his work circumstances and the high costs of Hajj?

Whoever makes a vow of devotion is obligated to fulfill it. Allah has praised those who fulfill their vows, as He Almighty said: "They fulfill [their] vows and fear a Day whose evil will be widespread." And the Prophet, peace be upon him, said: "Whoever vows to obey Allah, let him obey Him."

If the mother vowed to take her brother for Hajj and did not specify a time, then she must fulfill it whenever she finds the ability and her brother's work permits. If she specified a particular time and became financially unable or her brother could not go, then she is obligated to offer an expiation for a broken oath (kaffarat yamin). This is based on the Prophet's saying, peace be upon him: "And whoever makes a vow that he cannot fulfill, its expiation is the expiation for an oath. And whoever makes a vow that he can fulfill, let him fulfill it."

The expiation for a broken oath is: feeding ten needy persons or clothing them, or freeing a slave. If one cannot find [any of these], then fasting for three days.