Charles Ellicott Commentary Psalms 130:4

"But there is forgiveness with thee, That thou mayest be feared." — Psalms 130:4 (ASV)

But. —Rather, for, marking an ellipsis easily supplied. Israel’s sense of Jehovah’s readiness to forgive was too deep to need expression; it was understood: “You will not mark, etc., for ...”

Forgiveness. —The article in the original may be more than is common with abstract nouns: “The forgiveness we need.”

That you may be feared. —Either that the forgiven ones may become more profoundly religious, or perhaps, rather, that the manifestation of Divine mercy to Israel may strike fear in the nations.