Scripture proof: David at Keilah (1 Samuel 23) — God foreknew what Saul and the Keilites would do
They think it can be proved, both from the testimony of Scripture and from arguments of reason, that God has knowledge by which he foreknows with certainty things that would happen contingently under some condition.
From Scripture they first cite various examples of predictions about things that did not actually happen but would have happened had certain things been in place. One is 1 Samuel 23:11-12. David asked the Lord whether, if he stayed in the city of Keilah, Saul would come to capture him, and whether, if Saul came, the men of Keilah would hand him over to Saul. He was told both that Saul would come and that the men of Keilah would hand him over, if he stayed in Keilah.
So God foreknew with certainty both these things, which depended on the free will of Saul and of the men of Keilah, under a condition that never came about. David fled, and for that reason neither thing actually happened.
Latin
XII. Caeterum scientiam talem Deo convenire, qua certo praenoscat contingenter futura sub aliqua conditione, probari posse putant Scripturae testimoniis, & argumentis ex ratione ductis. Et primo quidem ex Scriptura proferunt varia exempla praedictionum de iis quae non contigerunt quidem, sed quae, positis his aut illis rebus, eventura erant: Quale est illud quod legitur 1 Sam. 23. v. 11, 12. Ubi quum David rogasset Dominum, An si in Urbe Kebela maneret, Saul venturus esset ad capiendum ipsum. Et si ille venisset, An Kebilitae ipsum tradituri essent in manum Saulis? responsum accepit & Saulem venturum, & Kebilitas ipsum in manum Saulis tradituros, si in urbe Kebila maneret. Ac proinde utrumque istud, quod a libera Saulis & Kehilitarum voluntate pendebat, certo praescivit Deus, sub conditione quae locum non habuit, David fugam arripiente, qua de causa neutrum revera factum est.