A New Testament example of God sending a strong delusion – 2 Thessalonian 2:9-12:
The coming of the lawless one is by the activity of Satan with all power and false signs and wonders, (10) and with all wicked deception for those who are perishing, because they refused to love the truth and so be saved. (11) Therefore God sends them a strong delusion, so that they may believe what is false, (12) in order that all may be condemned who did not believe the truth but had pleasure in unrighteousness.
This is not God sending or condoning a lie; it is God allowing those who refuse to love truth to believe what is false. God does not lie. Titus 1:2:
in hope of eternal life, which God, who never lies, promised before the ages began
We see other instances in the New Testament where God gave evil people up to the consequences of their actions and even hardened their already hard hearts:
What then? Israel failed to obtain what it was seeking. The elect obtained it, but the rest were hardened, (8) as it is written, “God gave them a spirit of stupor, eyes that would not see and ears that would not hear, down to this very day.”
Rom 1:18, 24-29, 32
(18)For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. … 24-29 Therefore God gave them up in the lusts of their hearts to impurity, to the dishonoring of their bodies among themselves, (25) because they exchanged the truth about God for a lie and worshiped and served the creature rather than the Creator, who is blessed forever! Amen. (26) For this reason God gave them up to dishonorable passions. For their women exchanged natural relations for those that are contrary to nature; (27) and the men likewise gave up natural relations with women and were consumed with passion for one another, men committing shameless acts with men and receiving in themselves the due penalty for their error. (28) And since they did not see fit to acknowledge God, God gave them up to a debased mind to do what ought not to be done. (29) They were filled with all manner of unrighteousness, evil, covetousness, malice. They are full of envy, murder, strife, deceit, maliciousness. They are gossips, … (32) Though they know God’s decree that those who practice such things deserve to die, they not only do them but give approval to those who practice them.
God does not want people to be in this mindset, as Psalm 81:11-13 makes very clear:
“But my people did not listen to my voice; Israel would not submit to me. (12) So I gave them over to their stubborn hearts, to follow their own counsels. (13) Oh, that my people would listen to me, that Israel would walk in my ways!
Notice in verse 13 that God wished his people would listen to Him. Paul explains a little about this subject in Romans 9:14-21:
What shall we say then? Is there injustice on God’s part? By no means! (15) For he says to Moses, “I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.” (16) So then it depends not on human will or exertion, but on God, who has mercy. (17) For the Scripture says to Pharaoh, “For this very purpose I have raised you up, that I might show my power in you, and that my name might be proclaimed in all the earth.” (18) So then he has mercy on whomever he wills, and he hardens whomever he wills. (19) You will say to me then, “Why does he still find fault? For who can resist his will?” (20) But who are you, O man, to answer back to God? Will what is molded say to its molder, “Why have you made me like this?” (21) Has the potter no right over the clay, to make out of the same lump one vessel for honorable use and another for dishonorable use?
So God who is merciful and is not willing that any should perish will use an evil person to achieve His purpose. This is a valid thing for God to do, because God is God. Unlike us, He knows in minute detail the motivations and intentions of people’s hearts and minds. He can judge justly and He does.
Let no one say when he is tempted, “I am being tempted by God,” for God cannot be tempted with evil, and he himself tempts no one. (14) But each person is tempted when he is lured and enticed by his own desire.