Its interpretation is as follows: if departure was not decreed for him, and yet he did not turn back from his intention to depart, but remained firmly resolved upon it, then in that case he is not required to repeat the prayer. When the matter is as we have mentioned, shortening remains binding upon him from that time until the completion of one month, unless he abandons his intention to travel during that period. This is because a person whose ruling is such is in the position of one who enters a town and does not know how long he will remain there. In that case, shortening remains binding upon him until the completion of one month, after which he must perform the prayer in full.
Commentary #13