After the creation we see that God was pleased ( Genesis 1:31 ). However, later in Genesis 6 we read "The LORD was grieved that he had made man on the earth, and his heart was filled with pain. So the LORD said, “I will wipe mankind, whom I have created, from the face of the earth – men and animals, and creatures that move along the ground, and birds of the air – for I am grieved that I have made them.” [NIV]
This is more like regret or sadness at having a perfect creation desecrated by sin ( man's doing, not God's ). I think you get into the freewill of man when you see God change His mind.
If we look at the story of the Golden Calf in Exodus 32 we read that God was so unhappy with his ‘stiff necked people’ that, in verse10, the Lord said to Moses, “Now leave me alone so that my anger may burn against them and that I may destroy them. Then I will make you into a great nation.” [NIV]
But Moses pleaded for his people and finally God said to Moses (v14): Then the LORD relented and did not bring on his people the disaster he had threatened.[NIV]
If we continue on with the story of the errant Israelites we find that God is still unhappy with them. In Exodus 33:3 God says: “Go up to the land flowing with milk and honey. But I will not go with you, because you are a stiff-necked people and I might destroy you on the way.” [NIV]
God is saying that He might not be able to control Himself because of the attitude of the Israelites. The freewill He has given us as the tool so that we can love Him as sons and daughters can also be turned against Him – it is a two-edged sword. With gifts like freewill comes responsibility. One cannot flourish without the other.
God is not going to manipulate us. He can say to us “I would like you to donate a certain sum of money for missionary work” but if we choose to ignore that ‘small still voice’ then God will get someone else to supply that need. Maybe you were His first choice but your own inaction had led God to find someone else.
Do you ever wonder how many times God had a task for you and you didn’t listen carefully? Do you ever think of lost opportunities to help someone find the Lord? Have you ever thought that maybe you should speak to someone about Jesus and then failed to do so, only to find out later that someone else led that person to the Lord?
God must change His mind because He is dealing with self-centred mortals who often get so wrapped up in their own petty problems that they neglect to listen to God. Because of our inability to be led, God must keep on finding alternatives to our lack of action. In light of this fact His will is still perfected on earth. He will have a body that serves and worships Him.
God does not change the laws and judgements of sin. His commandments do not change nor does the consequence of sinning. It has always been, and still is, spiritual death. His word is perfection and does not return unto Him void. Jesus made an excellent example when He said that the stones would cry out if the multitude of disciples had not done so ( Luke 19:40 ).
Look at another Scripture where God has changed His mind. In 1 Samuel 15:35b it says: And the LORD was grieved that he had made Saul king over Israel. [NIV] Again, man has let down God and God grieved His original decision to make Saul king. God did not make a mistake or let man down. In any case of God changing His mind we see that it is a result of man grieving Him by being disobedient or falling into sin.
In the case of Abraham ( concerning Sodom ) this was an exercise for the benefit of Abraham. Because of Abraham's faithfulness God ALLOWED Abraham to ask these things of Him.
In no way does this call into question God's infallability.
Not in any instance of God "changing His mind" do you see His prefection compromised. Even with the grief over Saul's rulership He still had a king. Even with the Israelites murmuring and complaining, He still kept His promises of deliverance.
One of the most remarkable stories in the Bible can be found in the book of Jonah (Jonah 1:1-4): The word of the LORD came to Jonah son of Amittai: “Go to the great city of Nineveh and preach against it, because its wickedness has come up before me.” But Jonah ran away from the LORD and headed for Tarshish. He went down to Joppa, where he found a ship bound for that port. After paying the fare, he went aboard and sailed for Tarshish to flee from the LORD. Then the LORD sent a great wind on the sea, and such a violent storm arose that the ship threatened to break up. [NIV] With the ship threatened, Jonah told the crew to throw him overboard to appease God and to save them. This they reluctantly did and the raging sea grew calm (v15). Jonah, of course, was swallowed by a “great fish” and stayed there for three days and nights. Finally, God “commanded the fish, and it vomited Jonah onto dry land” (Jonah 2:10).
Now let’s read from Jonah 3:1-4 Then the word of the LORD came to Jonah a second time: “Go to the great city of Nineveh and proclaim to it the message I give you.” Jonah obeyed the word of the LORD and went to Nineveh. Now Nineveh was a very important city – a visit required three days. On the first day, Jonah started into the city. He proclaimed: “Forty more days and Nineveh will be overturned.” [NIV] So Jonah finally obeyed the Lord and told the Ninevites that they had only 40 days before their huge city of more than 120,000 people would be overturned. Reading further from Jonah 3:5-10 The Ninevites believed God. They declared a fast, and all of them, from the greatest to the least, put on sackcloth. When the news reached the king of Nineveh, he rose from his throne, took off his royal robes, covered himself with sackcloth and sat down in the dust. Then he issued a proclamation in Nineveh: “By the decree of the king and his nobles: Do not let any man or beast, herd or flock, taste anything; do not let them eat or drink. But let man and beast be covered with sackcloth. Let everyone call urgently on God. Let them give up their evil ways and their violence. Who knows? God may yet relent and with compassion turn from his fierce anger so that we will not perish.” When God saw what they did and how they turned from their evil ways, he had compassion and did not bring upon them the destruction he had threatened. [NIV]
So the Ninevites repented of their “evil ways and their violence” and God, again, changed His mind. Why? Because of the reaction ( repentance )to His judgement of their sins. If anything, this last example sustains the concept of His perfection. God says that His mercies are everlasting. Had they repented and had He still destroyed them He would have been made a liar. He has always kept His word. Always. An imperfect man does not.