ويحتمل ان يكون الاتمام توجه إلى من دخل من سفره وكان قد دخل عليه الوقت وهو مسافر على ضرب من الاستحباب يدل على ذلك ما رواه
And it is possible that the instruction to complete (the prayer) was directed toward one who returned from his travel, and the time for the prayer had entered, while he was still traveling, as a form of recommendation (‘ala darb min al-istihbab’). What indicates that is what was narrated: