What does Scripture say about grace and free will (synergy)?

⁹ For we are God’s fellow workers. You are God’s farming, God’s building.

¹ Working together, we entreat also that you do not receive the grace of God in vain.

¹² So then, my beloved, even as you have always obeyed, not only in my presence, but now much more in my absence, work out your own salvation with fear and trembling. ¹³ For it is God who works in you both to will and to work for his good pleasure.

¹⁰ But by the grace of God I am what I am. His grace which was given to me was not futile, but I worked more than all of them; yet not I, but the grace of God which was with me.

¹⁵ Behold, I have set before thee this day life and death, good and evil. ¹⁶ If thou wilt hearken to the commands of the Lord thy God, which I command thee this day, to love the Lord thy God, to walk in all his ways, and to keep his ordinances, and his judgments; then ye shall live, and shall be many in number, and the Lord thy God shall bless thee in all the land into which thou goest to inherit it. ¹⁷ But if thy heart change, and thou wilt not hearken, and thou shalt go astray and worship other gods, and serve them, ¹⁸ I declare to you this day, that ye shall utterly perish, and ye shall by no means live long upon the land, into which ye go over Jordan to inherit it. ¹⁹ I call both heaven and earth to witness this day against you, I have set before you life and death, the blessing and the curse: choose thou life, that thou and thy seed may live; ²⁰ to love the Lord thy God, to hearken to his voice, and cleave to him; for this [is] thy life, and the length of thy days, that thou shouldest dwell upon the land, which the Lord sware to thy fathers, Abraam, and Isaac, and Jacob, to give to them.

¹⁵ But if it seem not good to you to serve the Lord, choose to yourselves this day whom ye will serve, whether the gods of your fathers that were on the other side of the river, or the gods of the Amorites, among whom ye dwell upon their land: but I and my house will serve the Lord, for he is holy.

¹⁴ He himself made man from the beginning, and left him in the hand of his counsel; ¹⁵ if thou wilt, to keep the commandments, and to perform acceptable faithfulness. ¹⁶ He hath set fire and water before thee: stretch forth thy hand unto whether thou wilt. ¹⁷ Before man is life and death; and whether he liketh shall be given him.

³⁰ I will judge you, O house of Israel, saith the Lord, each one according to his way: be converted, and turn from all your ungodliness, and it shall not become to you the punishment of iniquity. ³¹ Cast away from yourselves all your ungodliness wherein ye have sinned against me; and make to yourselves a new heart and a new spirit: for why should ye die, O house of Israel? ³² For I desire not the death of him that dies, saith the Lord.

³ For this is good and acceptable in the sight of God our Savior, ⁴ who desires all people to be saved and come to full knowledge of the truth.

⁹ The Lord is not slow concerning his promise, as some count slowness; but he is patient with us, not wishing that anyone should perish, but that all should come to repentance.

¹¹ Say to them, Thus saith the Lord; [As] I live, I desire not the death of the ungodly, as that the ungodly should turn from his way and live: turn ye heartily from your way; for why will ye die, O house of Israel?

³⁷ “Jerusalem, Jerusalem, who kills the prophets and stones those who are sent to her! How often I would have gathered your children together, even as a hen gathers her chicks under her wings, and you would not!

²⁰ Behold, I stand at the door and knock. If anyone hears my voice and opens the door, then I will come in to him and will dine with him, and he with me.

⁴⁴ No one can come to me unless the Father who sent me draws him; and I will raise him up in the last day.

⁵ I am the vine. You are the branches. He who remains in me and I in him bears much fruit, for apart from me you can do nothing.

¹⁶ You didn’t choose me, but I chose you and appointed you, that you should go and bear fruit, and that your fruit should remain; that whatever you will ask of the Father in my name, he may give it to you.

¹ You were made alive when you were dead in transgressions and sins, ² in which you once walked according to the course of this world, according to the prince of the power of the air, the spirit who now works in the children of disobedience. ³ We also all once lived among them in the lusts of our flesh, doing the desires of the flesh and of the mind, and were by nature children of wrath, even as the rest. ⁴ But God, being rich in mercy, for his great love with which he loved us, ⁵ even when we were dead through our trespasses, made us alive together with Christ—by grace you have been saved—

¹⁴ A certain woman named Lydia, a seller of purple, of the city of Thyatira, one who worshiped God, heard us. The Lord opened her heart to listen to the things which were spoken by Paul.

²⁸ We know that all things work together for good for those who love God, for those who are called according to his purpose. ²⁹ For whom he foreknew, he also predestined to be conformed to the image of his Son, that he might be the firstborn among many brothers. ³⁰ Whom he predestined, those he also called. Whom he called, those he also justified. Whom he justified, those he also glorified.

¹⁰ Not only so, but Rebekah also conceived by one, by our father Isaac. ¹¹ For being not yet born, neither having done anything good or bad, that the purpose of God according to election might stand, not of works, but of him who calls, ¹² it was said to her, “The elder will serve the younger.” ¹³ Even as it is written, “Jacob I loved, but Esau I hated.” ¹⁴ What shall we say then? Is there unrighteousness with God? May it never be! ¹⁵ For he said 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 is not of him who wills, nor of him who runs, but of God who has mercy. ¹⁷ For the Scripture says to Pharaoh, “For this very purpose I caused you to be raised up, that I might show in you my power, and that my name might be proclaimed in all the earth.” ¹⁸ So then, he has mercy on whom he desires, and he hardens whom he desires. ¹⁹ You will say then to me, “Why does he still find fault? For who withstands his will?” ²⁰ But indeed, O man, who are you to reply against God? Will the thing formed ask him who formed it, “Why did you make me like this?” ²¹ Or hasn’t the potter a right over the clay, from the same lump to make one part a vessel for honor, and another for dishonor? ²² What if God, willing to show his wrath and to make his power known, endured with much patience vessels of wrath prepared for destruction, ²³ and that he might make known the riches of his glory on vessels of mercy, which he prepared beforehand for glory— ²⁴ us, whom he also called, not from the Jews only, but also from the Gentiles?

³ Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ, ⁴ even as he chose us in him before the foundation of the world, that we would be holy and without defect before him in love, ⁵ having predestined us for adoption as children through Jesus Christ to himself, according to the good pleasure of his desire, ⁶ to the praise of the glory of his grace, by which he freely gave us favor in the Beloved. ⁷ In him we have our redemption through his blood, the forgiveness of our trespasses, according to the riches of his grace ⁸ which he made to abound toward us in all wisdom and prudence, ⁹ making known to us the mystery of his will, according to his good pleasure which he purposed in him ¹⁰ to an administration of the fullness of the times, to sum up all things in Christ, the things in the heavens and the things on the earth, in him. ¹¹ We were also assigned an inheritance in him, having been foreordained according to the purpose of him who does all things after the counsel of his will,

⁴⁸ As the Gentiles heard this, they were glad and glorified the word of God. As many as were appointed to eternal life believed.