John Calvin Commentary Numbers 25:1

"And Israel abode in Shittim; and the people began to play the harlot with the daughters of Moab:" — Numbers 25:1 (ASV)

And Israel abode in Shittim. From this narrative we learn certainly that the people were no more able to bear prosperity than adversity. Previously, whether worn out by fatigue or made impatient by abstinence and famine, they had often rebelled against God. Now, having entered a habitable land and resting in the midst of fruitful fields, they were incited by their more comfortable dwellings and pleasant way of life to lasciviousness and the indulgence of filthy lusts.

Moses relates how, when they had given way to their lust, they fell at the same time into whoredom and idolatry. We will soon see that this arose from Balaam’s counsel: that the Moabites should prostitute their women to the Israelites to entice them with their enticements to unholy worship.

Balaam had learned by experience that God’s favor was an invincible safeguard, protecting the people from all injury. He therefore devised a plan by which they might destroy themselves, not only by depriving themselves of God’s protection but also by provoking His wrath against them. By this device, then, Balaam stirred up the fire that impelled these poor wretches, inflamed by blind lechery, to another crime by which they might arouse God’s hostility against themselves.

Consequently, Paul, referring to this history, informs us that the punishment, which will be mentioned shortly, was inflicted upon them for fornication (1 Corinthians 10:8). For although it was God’s design to avenge the violation of His worship, it is still fitting to examine the origin and source of the evil.

Just as, if a drunken man kills a person, the murder will be imputed to his drunkenness, so Paul, seeing the Israelites impelled by fornication to idolatry, presents the punishment to us as a warning to deter us from fornication. This sin was the primary cause of their punishment and the means of their corruption.

Since, then, the fall from one sin to another is so easy, let us therefore learn to be more watchful, so that Satan does not entangle us in his snares. Let us also observe that he creeps up on us by degrees to entrap us.

The Moabite young women did not immediately ask the Israelites to worship their idols. Instead, they first invited them to their banquets, thus tempting them to idolatry. For if idol worship had been mentioned at first, perhaps the Israelites would have shuddered at the heinousness of the crime, to which they allowed themselves to be gradually deceived.

Now, to be present at a feast celebrated in honor of false gods was a kind of indirect renunciation of the true God. And when they had been attracted this far, they threw aside all shame and abandoned themselves to that extreme act by which they transferred the honor due only to the one true God to false and imaginary deities.