Albert Barnes Commentary Psalms 106:21-22

"They forgat God their Saviour, Who had done great things in Egypt, Wondrous works in the land of Ham, [And] terrible things by the Red Sea." — Psalms 106:21-22 (ASV)

They forgot God their Savior ... - The God who had saved, or delivered them, out of Egypt. The sentiment here is the same as in Psalms 78:11-12. See the notes at that place.