Charles Ellicott Commentary Psalms 18:30

"As for God, his way is perfect: The word of Jehovah is tried; He is a shield unto all them that take refuge in him." — Psalms 18:30 (ASV)

Tried. —“Sterling gold,” not dross. (and for “shield,”Psalms 5:12.)Proverbs 30:5 seems to be taken from this verse.