Free will is about choice. And there are plenty of places in the bible where we can see that, starting in the garden.
But here is a place in the Torah where the servant of God is speaking directly to his people right before they go into the promised land.
See, I have set before thee this day life and good, and death and evil;
16 In that I command thee this day to love the LORD thy God, to walk in his ways, and to keep his commandments and his statutes and his judgments, that thou mayest live and multiply: and the LORD thy God shall bless thee in the land whither thou goest to possess it.
17 But if thine heart turn away, so that thou wilt not hear, but shalt be drawn away, and worship other gods, and serve them;
18 I denounce unto you this day, that ye shall surely perish, and that ye shall not prolong your days upon the land, whither thou passest over Jordan to go to possess it.
19 I call heaven and earth to record this day against you, that I have set before you life and death, blessing and cursing: therefore choose life, that both thou and thy seed may live:
20 That thou mayest love the LORD thy God, and that thou mayest obey his voice, and that thou mayest cleave unto him: for he is thy life, and the length of thy days: that thou mayest dwell in the land which the LORD sware unto thy fathers, to Abraham, to Isaac, and to Jacob, to give them.
Just like today, they were given a choice to obey God (and live) or to not (and die).
He created us with Free will, the choice to love him or not.