This narration is to be understood as referring to the case when he enters (his home) and the time (for the prayer) still remains then it becomes obligatory upon him to perform it in full. But as for when the time has passed, then it is not obligatory upon him to make it up except in the manner it was missed. Likewise, if he set out for travel while the time still remained, then shortening (the prayer) is obligatory upon him. And what indicates this is what was narrated:
Commentary #7