Allah (swt) swears by what He wills to what He wills. Here Allah (swt) swears by one of His creations, that perform a task to humans, that are (the racers, panting) whether they are racers in fight, doing good deed or worship act. Some interpreted it as being the pilgrimage caravan. An oath always comes to confirm what is sworn to, which is usually controversial. The answer of this oath is three matters indicated in the following verses (6-8).
وَالْعَادِيَاتِ (racers): The horses running forward for the cause of Allah (swt) in battles against the enemies. It refers, as well, to the camels that are running from A’rafat to Muzdalifah in the pilgrimage, and from Muzdalifah to Mina.
ضَبْحًا (panting): Sound of the horse’s breath, neither neighing nor whining.
Thereof, Allah (swt) swears by the horses in the battle fields or by the camels in the sacred places.