John Gill Commentary Psalms 118:4

"Let them now that fear Jehovah say, That his lovingkindness [endureth] for ever." — Psalms 118:4 (ASV)

Let them now that fear the Lord say, that his mercy [endures]
for ever .
] Not the proselytes to the Jewish religion only, but all that feared the Lord among all people, as Aben Ezra observes; such as fear the Lord and his goodness, and have had an experience of his grace and mercy, which has caused them to fear him; and to whom the mercy of God is great, and on whom it is from everlasting to everlasting; and therefore should speak well of it, and set their seal to it, that it abides for ever; see (Psalms 103:11Psalms 103:17) .