What are the rulings on vows?

Question:
This person asks and says: I am sick and I came to perform 'Umrah. I am suffering from asthma and am sensitive to the cold. I came to perform 'Umrah and I made a vow to Allah that if I complete the 'Umrah safely and no illness befalls me, I will observe i'tikaf (spiritual retreat in the mosque) for one day in the Sacred Mosque. I note that I do not know the prescribed time for i'tikaf.

Answer:
Yes, this is a vow of obedience, and you must fulfill it. The Prophet (peace and blessings be upon him) said: It is a vow of obedience, so you must observe i'tikaf on the day you vowed. If it was a specific day, then you observe it on that day. If it was not a specific day, you observe i'tikaf on any day that is convenient for you. This is obligatory upon you.