Albert Barnes Commentary Psalms 18:13

"Jehovah also thundered in the heavens, And the Most High uttered his voice, Hailstones and coals of fire." — Psalms 18:13 (ASV)

The Lord also thundered in the heavens - Thunder is often in the Scriptures described as the voice of God. See the magnificent description in (Psalms 29:1–11); compare (Job 40:9), Canst thou thunder with a voice like him? So (1 Samuel 7:10); (1 Samuel 12:18); (Psalms 77:18); (Job 37:4).

And the Highest gave his voice - God, the most exalted Being in the universe, uttered his voice in the thunder; or, the thunder was his voice.

Hail-stones, and coals of fire - Accompanying the thunder. The repetition seems to be because these were such striking and constant accompaniments of the storm.