But were mingled He describes what was the result of this foolish humanity; namely, that they were defiled with the pollutions of the nations whom they had spared. Had they exclusively inhabited the land of Canaan, they would have more easily retained the pure worship of God. Allured by the influence of such neighbors, it is not wonderful that they soon degenerated from the footsteps of their fathers, for we are more inclined to follow the example of the bad than of the good. And now he speaks of the descendants of those who had so frequently provoked God's anger in the wilderness, and declares, that as the same unbelief, rebellion, and ingratitude, were rampant in the succeeding race, they were no better than their fathers. In mingling with the heathens they openly rejected the distinguishing loving-kindness of God, who adopted them as his children, under the express condition that they should be separated from these profane nations. Therefore, in associating with them indiscriminately, they render this holy covenant of no effect. When he adds, that they learned their works, he warns us, that nothing is more dangerous than associating with the ungodly; because, being more prone to follow vice than virtue, it cannot but be, that the more conversant we are with corruption, the more widely will it spread. In such circumstances, the utmost care and caution are requisite, lest the wicked, with whom we come into contact, infect us by their vitiated morals; and particularly where there is danger of relapsing into idolatry, to which we are all naturally prone. What, then, will be the effect produced upon us when instigated by others to commit sin, but to add sin to sin? The prophet, therefore, declares that the Jews were already so much under the tuition of the heathen as to abandon themselves to the practice of their idolatrous rites. In employing the word to serve, he confutes the contemptible evasion of the Papists, who pretend that they do not give to images the worship that is due to God alone, but only a sort of honorary adoration. But if the worshipping of images be lawful, the prophet had no sufficient cause to condemn his own nation for serving strange gods. Despicable, therefore, is the distinction, that Divine homage is to be paid to God alone, and that a kind of honorary adoration is to be given to images. He adds, that this issued in their overthrow, in order that their obstinate attachment to their follies, and their despising the chastisements of God, may more palpably appear.

But were mingled among the heathen - Among the nations; by intermarriage, and by commerce. They suffered them to remain in the land, contrary to the command of God, and thus greatly exposed and endangered the purity of their religion and their own morals. See Judges 2:2; Judges 3:5-6.
And learned their works - Their practices; their customs and habits: learned to live as they did. This was an illustration of the danger of contact with the wicked and the worldly. What occurred in their case has often occurred since in the history of the people of God, that by "mingling" with the world they have learned to practice their "works;" have become conformed to their manner of living, and have thus lost their spirituality, and brought dishonor on the cause of religion. There is some proper sense in which the people of God are not to be conformed to the world; in which, though living among them, they are to be separate from them; in which, though they are parts of the same nation, and live under the same government and laws, they are to be a distinct and special people, ruled supremely by higher laws, and having higher and nobler ends of life. Romans 12:2; 2-Corinthians 6:14-17.

But were mingled among the Heathen,.... Not only dwelt among them, but made covenants and contracts, carried on trade and commerce, and intermarried with them, contrary to the express law of God, Deuteronomy 7:2. Nor should saints have communion with wicked men, especially in things sinful and superstitious, 2-Corinthians 6:14.
And learned their works; not their civil works and actions, their trades and business, but their idolatrous works; of which a detail is given in the following verses: "evil communications corrupt good manners", 1-Corinthians 15:33.