Is it a condition that the one performing i'tikaf (spiritual retreat in the mosque) specifies the duration of his retreat?

Question:
This questioner says: Does the one performing i'tikaf have to specify the duration he intends to retreat for, or can he retreat without specifying a duration? He retreats without specifying a duration.

Answer:
He retreats without specifying a duration, and he exits whenever he wishes, unless he has made a vow. See, if he has vowed a specific duration, he must complete it, as the Messenger of Allah (peace and blessings be upon him) said: But if he has not vowed i'tikaf and is only doing it voluntarily, then he retreats as long as he wishes—whether a long, short, or medium retreat. He retreats as long as he wishes, and he receives reward according to the length of his retreat.