James 1:13
Let no one say when he is tempted, ‘I am being tempted by God’; for God cannot be tempted by evil, and He Himself does not tempt anyone.
God tests people concerning sin, but does not tempt people to commit sin. That’s a critical difference. To test is to measure, but to tempt is to try to get someone to do something. God does not try to get anyone to sin. God may use man’s sin, but God does not try to get man to sin. But, if, as alleged by Calvinists, that God has a particular “purpose in sin,” and not just any random sin, but very precise sins, then He has a need, both for those precise sins to be enacted, and the means by which to get them enacted, which would otherwise need to be through a temptation.
Dave Hunt comments: “God allows evil and can prevent, control, or use it, even for good (Genesis 50:20), but He doesn’t even tempt anyone to evil (James 1:13), much less decree it.” (Debating Calvinism, p.327, emphasis mine)
According to Calvinism, God did decree sin, and sin is a something, and God decreed everything:
John Calvin writes: “But the objection is not yet resolved, that if all things are done by the will of God, and men contrive nothing except by His will and ordination, then God is the author of all evils.” (Concerning the Eternal Predestination of God, p.179, emphasis mine)
Calvin writes: “Thinking that the difficulty here may be resolved by a single word, some are foolish enough serenely to overlook what occasions the greatest ambiguity; namely, how God may be free of guilt in doing the very thing that He condemns in Satan and the reprobate and which is to be condemned by men.” (Concerning the Eternal Predestination of God, p.179, emphasis mine)
Calvin writes: “We learn that nothing happens but what seems good to God. How then is God to be exempted from the blame to which Satan with his instruments is liable?” (Concerning the Eternal Predestination of God, p.180, emphasis mine)
Calvin writes: “What I have maintained about the diversity of causes must not be forgotten: the proximate cause is one thing, the remote cause another.” (Concerning the Eternal Predestination of God, p.181, emphasis mine)
Calvin writes: “Certain shameless and illiberal people charge us with calumny by maintaining that God is made the author of sin, if His will is made first cause of all that happens. For what man wickedly perpetrates, incited by ambition or avarice or lust or some other depraved motive, since God does it by his hand with a righteous through perhaps hidden purpose--this cannot be equated with the term sin.” (Concerning the Eternal Predestination of God, p.181, emphasis mine)