Majma al-Zawaid — Hadith 11515

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) sent out some horsemen. A month passed, but no news came from them. Then this surah was revealed: "By those that run with panting breath from their chests." (Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says:) That is, the sound comes from their feet. "Those that strike out fire from the stones with their hooves." Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: That is, they strike their hooves on the stones and sparks fly from them. "And by those that raid at dawn." Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: That is, they attack the enemy in the morning. "Then they raise up dust." Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: That is, they raise up the dust with their hooves. "And then they penetrate into the midst of the enemy." Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: That is, the enemy has gathered together (or: they penetrate into the midst of the enemy).
Al-Bazzar recorded it; its chain contains Hafs bin Jumay', who is da'if (weak).