Free will is a concept often taken for granted in the Christian world. It answers the "problem" of evil. The only possible way God can be perfectly good and yet evil can still exist in His "very good" (Genesis 1:31), perfect (Deuteronomy 32:4) creation is if free will exists. Surprisingly, there are a large number of Christians who do not believe free will exists, and will actually argue vehemently against it.
In the header image, I have briefly examined a few verses that show that free will exists, which I'll expand on in a moment, but first, I want to suggest that the only logical way for us to even have this discussion is if free will exists. If free will does not exist, it makes no sense to have the discussion, because those who believe in free will are not free to stop believing in free will. Of course, those who don't believe in free will are also not free to not have the discussion, so although it is irrational, it's also inevitable. This is certainly not the rational God we serve. Without further ado, whether by our own choice or because we are being controlled by external forces, let's look at the Biblical evidence for free will.
In Jeremiah 26:3, we read "Perhaps everyone will listen and turn from his evil way, that I may relent concerning the calamity which I purpose to bring on them because of the evil of their doings.’"
That key word, "perhaps", indisputably proves that free will exists. Even on its own, the word "perhaps" indicates that there are at least two possibilities: Repentance and forgiveness, or sin and judgement. Thus, God must have been leaving it up to the Israelites whether or not they would continue in, or repent of, their rebellion.
Furthermore, we know that God knows what will happen before it happens. He declares the end from the beginning (Isaiah 46:10), so He knew full well whether or not Israel would have repented for hearing Jeremiah's words. How could He possibly have said perhaps they would repent, not only knowing that they wouldn't (they didn't), but that they actually couldn't? There are only two possibilities: God is a liar, or the Israelites really were free to repent. I hope I don't need to explain why the former possibility is problematic, to put it charitably.
In Luke 7:30, we read "But the Pharisees and lawyers rejected the will of God for themselves, not having been baptized by him."
Here we have clear proof that God has one will, and man can have another. We can reject God's will for ourselves. Now, this is where people who don't believe in free will will accuse me of blasphemy (blasphemy which, apparently, I don't have the freedom to avoid committing). However, we need to establish the relationship between free will and God's sovereignty.
Think of it this way. We know that the men who arrested Jesus were weaker than Jesus. Jesus, aside from being God Himself, also explicitly said "Or do you think that I cannot now pray to My Father, and He will provide Me with more than twelve legions of angels?" (Matthew 26:53). So, does the fact that the Jews and Romans successfully arrested, beat up and eventually killed Jesus mean they were stronger than Jesus? Of course not! It means He allowed them to. In the same way, the Pharisees and lawyers who rejected the will of God did not overwhelm Him. He gave them the freedom to reject His will. He could take it back in a heartbeat. Nevertheless, the fact that the Bible itself says these men rejected God's will shows that they had the freedom to do so. The only alternative is that these men genuinely were stronger than God, which is actual blasphemy.
In James 1:13, we read "Let no one say when he is tempted, “I am tempted by God”; for God cannot be tempted by evil, nor does He Himself tempt anyone."
Who can man blame for temptation? Not God. But if temptation does not come from God, it must come from a source that is not God. James goes on to tell us that each is tempted when he is drawn away by his own desires. Thus, evil can only exist in a world with free will.
In 2 Peter 3:9, we read "The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance." Although they're separated in the header image (poor planning on my part), I'm also going to quote Ezekiel 18:32 and 33:11 here:
"For I have no pleasure in the death of one who dies,” says the Lord God. “Therefore turn and live!”" (18:32). "Say to them: ‘As I live,’ says the Lord God, ‘I have no pleasure in the death of the wicked, but that the wicked turn from his way and live. Turn, turn from your evil ways! For why should you die, O house of Israel?’" (33:11).
It is abundantly clear that death, whether we're speaking physical death or the "second death", isn't something God is especially fond of. It's just something He has to do because it's not in His nature to tolerate sin. But He takes no pleasure in it. In other words, it's not in His will. In fact, those aren't even other words, His exact words are that He is "not willing that any should perish but that all should come to repentance." If God wills that all should come to repentance, but not all will come to repentance, that shows that God's will is not the only will in play. Again, this does not mean that He is incapable of enforcing His own will, but rather He willingly surrenders His own will in order for His glory to manifest itself.
In Numbers 14:11, we read "Then the Lord said to Moses: “How long will these people reject Me? And how long will they not believe Me, with all the signs which I have performed among them?"
This is just one example of God asking "how long?" There are many others. If we have free will, this makes sense. Although God knows exactly how long it will be, He asks rhetorically for our sake. But if we don't have free will, God is effectively asking "how long will it be before I stop forcing you to disobey me?" Where's the logic in that?
In Proverbs 16:9, we read "A man’s heart plans his way, But the Lord directs his steps."
This verse further establishes the relationship between free will and God's sovereignty. Whereas those who reject free will argue that the existence of free will would undermine God's sovereignty because it makes man "stronger" than God, this verse shows us that God is too strong to be hindered by man's free will. As Master Oogway said in Kung Fu Panda, "we often find our destiny on the path we take to avoid it". You can make as many plans in your heart as you want, that doesn't make a dent in God's own plans.
In Esther 4:14, we read "For if you remain completely silent at this time, relief and deliverance will arise for the Jews from another place, but you and your father’s house will perish. Yet who knows whether you have come to the kingdom for such a time as this?”"
Similar to Proverbs 16:9, this verse shows that God is capable of achieving His goals regardless of what your goals are. However, Esther 4:14 has the added element of establishing just how glorious it is to obey. God doesn't owe us anything. He doesn't have to include us in His plans at all. So we can choose not to be a part of them. Either way, God wins, but only if we obey do we win with Him. Free will does not contradict God's sovereignty.
In Joshua 24:15, we read "And if it seems evil to you to serve the Lord, choose for yourselves this day whom you will serve, whether the gods which your fathers served that were on the other side of the River, or the gods of the Amorites, in whose land you dwell. But as for me and my house, we will serve the Lord.”"
How could Joshua tell Israel to choose between the false gods and the real God if they could not choose between the two? Choosing is the literal definition of free will, so either God lied through Joshua, or Joshua meant choose when he said choose.
In Deuteronomy 30:19, we read "I call heaven and earth as witnesses today against you, that I have set before you life and death, blessing and cursing; therefore choose life, that both you and your descendants may live;"
This isn't just a feeble human prophet talking. This is God Himself saying choose between the two options He presented. Sin and death, or obedience and life. We've got the choice.
In 1 Corinthians 10:13, we read "No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it."
We already know from James 1:13 that God doesn't tempt anyone, so it's very likely that this verse applies to all humans anyway, however even if we only assume this applies to Christians, the fact remains that it indisputably proves Christians can resist all temptation. And yet none of us do this all the time. God's giving us the ability to bear it, yet we don't always bear it. Necessary conclusion: Christians have free will. With the aforementioned James 1:13, we have no reason to assume this is limited to Christians.
All of these verses, and more, show indisputably that free will exists. It's the only explanation for why evil exists, for why the Bible not only suggests that people can reject God's will, but even gives an example of people who did, and for why God ultimately acts as if we have free will. Free will also does not contradict God's sovereignty. Far from it, God's sovereignty is made significantly more glorious by the fact we have free will. Those who reject the existence of free will have an uphill battle to fight. It's their choice whether or not to fight it.