This goes back to their furious speed. They are charging at such speeds that dust clouds form because of it. It could also refer to the horse-riders who raise these dust clouds by commanding their steeds to charge so furiously.
Raids are normally carried out during the night but this one is happening in plain sight - in the morning. These horses are doing things that are very attention catching
and give off clear signs to the enemy that they are about to be raided. Firstly by charging furiously and at such a speed that sparks of fire are flying out. Secondly, by raiding in broad daylight and thirdly, by creating huge and visible clouds of dust. All these things are enough for the enemy to know beforehand that they are about to be raided. This is important to note in the context of this surah.
Stirred up, with it, dust clouds
Commentary covering verses 3–4
This goes back to their furious speed. They are charging at such speeds that dust clouds form because of it. It could also refer to the horse-riders who raise these dust clouds by commanding their steeds to charge so furiously.
Raids are normally carried out during the night but this one is happening in plain sight - in the morning. These horses are doing things that are very attention catching
and give off clear signs to the enemy that they are about to be raided. Firstly by charging furiously and at such a speed that sparks of fire are flying out. Secondly, by raiding in broad daylight and thirdly, by creating huge and visible clouds of dust. All these things are enough for the enemy to know beforehand that they are about to be raided. This is important to note in the context of this surah.