As you can imagine it was a hard but rewarding read, plus I read it in the Banner of Truth edition and nearly lost my eyesight in the process.
Edwards has a brilliant section (XI) on "The Evidence of God's Certain Foreknowledge of the Volitions of Moral Agents." He has an interesting caveat before he builds his case from Scripture:
One would think it wholly needless to enter on such an argument with any that profess themselves Christians: but so it is; God's certain foreknowledge of the free acts of moral agents, is denied by some that pretend to believe the Scriptures to be the Word of God; and especially of late. I therefore shall consider the evidence of such a prescience in the Most High...
My first argument shall be taken from God's prediction of such events. Here I would, in the first place, lay down these two things as axioms.
1. If God does not foreknow, He cannot foretell such events; that is, He cannot peremptorily and certainly foretell them. If God has no more than an uncertain guess concerning events of this kind, then he can declare no more than an uncertain guess. Positively to foretell, is to profess to foreknow, or declare positive foreknowledge.
2. If God does not certainly foreknow the future volitions of moral agents, then neither can he certainly foreknow those events which are dependent on these volitions. The existence of the one depending on the existence of the other, the knowledge of the existence of the one depends on the knowledge of the existence of the other; and the one cannot be more certain than the other.