Often misinterpreted, God's foreknowledge is critical to a right understanding to the Gospel. Without a correct understanding of it the Sovereign gift God mutates into works righteousness. A.W. Pink clarifies for us:
Let us pause and define our terms. What is meant by “foreknowledge”? “To know beforehand,” is the ready reply of many. But we must not jump to conclusions, nor must we turn to Webster’s dictionary as the final court of appeal, for it is not a matter of the etymology of the term employed. What is needed is to find out how the word is used in Scripture. The Holy Spirit’s usage of an expression always defines its meaning and scope. It is failure to apply this simple rule which is responsible for so much confusion and error.
...Now the word “foreknowledge” as it is used in the New Testament is less ambiguous than in its simple form “to know.” If every passage in which it occurs is carefully studied, it will be discovered that it is a moot point whether it ever has reference to the mere perception of events which are yet to take place. The fact is that “foreknowledge” is never used in Scripture in connection with events or actions; instead, it always has reference to persons. It is persons God is said to “foreknow,” not the actions of those persons.
...The first occurrence is in Acts 2:23. There we read, “Him being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain.” If careful attention is paid to the wording of this verse, it will be seen that the Apostle was not there speaking of God’s foreknowledge of the act of the crucifixion, but of the Person crucified: “Him (Christ) being delivered by,” etc.
The second occurrence is in Rom. 8:29, 30. “For whom He did foreknow, He also did predestinate to be conformed to the image of His Son, that He might be the Firstborn among many brethren. Moreover whom He did predestinate, them He also called,” etc. Weigh well the pronoun that is used here. It is not what He did foreknow, but whom He did. It is not the surrendering of their wills nor the believing of their hearts, but the persons themselves that are here in view.
...The last mention is in 1 Peter 1:2: “Elect according to the foreknowledge of God the Father.” Who are “elect according to the foreknowledge of God the Father”? The previous verse tells us: the reference is to the “strangers scattered” i. e. the Diaspora, the Dispersion, the believing Jews. Thus, here too the reference is to persons, and not to their foreseen acts.
Now in view of these passages (and there are no more) what scriptural ground is there for anyone saying God “foreknew” the acts of certain ones, viz., their “repenting and believing,” and that because of those acts He elected them unto salvation? The answer is, None whatever. Scripture never speaks of repentance and faith as being foreseen or foreknown by God. Truly, He did know from all eternity that certain ones would repent and believe, yet this is not what Scripture refers to as the object of God’s “foreknowledge.” The word uniformly refers to God’s foreknowing persons; then let us “hold fast the form of sound words” (2 Tim. 1:18).
...It thus appears that it is highly important for us to have clear and scriptural views of the “foreknowledge” of God. The popular idea of Divine foreknowledge is not only inadequate and erroeneous, but slanders the reality of God’s attributes, bringing Him disgrace rather than the glory which is His due. God not only knew the end from the beginning, but He planned, fixed, predestinated everything from the beginning. And, as cause stands to effect, so God’s purpose is the ground of His prescience. If then the reader be a real Christian, he is so because God chose him in Christ before the foundation of the world (Eph. 1:4), and chose not because He foresaw you would believe, but chose simply because it pleased Him to choose; chose you notwithstanding your natural unbelief. This being so, all the glory and praise belongs alone to Him. You have no ground for taking any credit to yourself. You have “believed through grace” (Acts 18:27), and that, because your very election was “of grace” (Rom. 11:5). (From the Attributes of God by A.W. Pink.)