John Gill Commentary Psalms 78:56

"Yet they tempted and rebelled against the Most High God, And kept not his testimonies;" — Psalms 78:56 (ASV)

Yet they tempted and provoked the most high God
After the death of Joshua, and in the times of the judges, by worshipping and serving the gods of the nations, and forsaking the Lord their God, who had done such great things for them, (Judges 2:11–14),

and kept not his testimonies;
the laws of God, which testified and declared his mind and will; nor observed his word and ordinances, which testified of his grace, and of the way of salvation by Jesus Christ.