Charles Ellicott Commentary Psalms 106:34-39

"They did not destroy the peoples, As Jehovah commanded them, But mingled themselves with the nations, And learned their works, And served their idols, Which became a snare unto them. Yea, they sacrificed their sons and their daughters unto demons, And shed innocent blood, Even the blood of their sons and of their daughters, Whom they sacrificed unto the idols of Canaan; And the land was polluted with blood. Thus were they defiled with their works, And played the harlot in their doings." — Psalms 106:34-39 (ASV)

The national sin after the settlement in Canaan.