John Calvin Commentary Psalms 106:39

"Thus were they defiled with their works, And played the harlot in their doings." — Psalms 106:39 (ASV)

And they were polluted with their own works. He now concludes by stating generally that the Jews, by adopting the abominable practices of the heathen, had become entirely filthy, because in all human devices there is nothing but impurity. He calls works of men all the false worship that they devise without Divine sanction, as if to say that the holiness truly connected with the worship of God comes from His word, and that all human inventions and admixtures in religion are profane and tend to corrupt the service of God.

Doubtless, it was the Israelites' intention to serve God, but the Holy Spirit declares that all the fruit of their burning zeal was their becoming more abominable in God’s sight by their lewd inventions. For a strict adherence to the word of God constitutes spiritual chastity.