Charles H. Spurgeon on Psalms 106:39

Thus were they defiled with their own works, and went a whoring with their own inventions. Not only the land but the inhabitants of it were polluted. They broke the marriage bond between them and the Lord, and fell into spiritual adultery. The language is strong, but the offence could not be fitly described in less forcible words. As a husband is deeply dishonoured and sorely wounded should his wife become unchaste and run riot with many paramours in his own house, so was the Lord incensed at his people for setting up gods many and lords many in his own land. They made and invented new gods, and then worshipped what they had made. What a folly! Their novel deities were loathsome monsters and cruel demons, and yet they paid them homage. What wickedness! And to commit this folly and wickedness they cast off the true God, whose miracles they had seen, and whose people they were. This was provocation of the severest sort.

Verses 40. Therefore was the wrath of the LORD kindled against his people, in so much that he abhorred his own inheritance. Not that even then he broke his covenant or utterly cast off his offending people, but he felt the deepest indignation, and even looked upon them with abhorrence. The feeling described is like to that of a husband who still loves his guilty wife, and yet when he thinks of her lewdness feels his whole nature rising in righteous anger at her, so that the very sight of her afflicts his soul. How far the divine wrath can burn against those whom he yet loves in his heart it were hard to say, but certainly Israel pushed the experiment to the extreme. And he gave them into the hand of the heathen. This was the manifestation of his abhorrence. He gave them a taste of the result of sin; they spared the heathen, mixed with them and imitated them, and soon they had to smart from them, for hordes of invaders were let loose upon them to spoil them at their pleasure. Men make rods for their own backs. Their own inventions become their punishments. And they that hated them ruled over them. And who could wonder? Sin never creates true love. They joined the heathen in their wickedness, and they did not win their hearts, but rather provoked their contempt. If we mix with men of the world they will soon become our masters and our tyrants, and we cannot want worse.