You are right to point out the grammar, “this” refers to the entire statement: “It is by grace that you have been saved, through faith”. However, this does, in fact, mean that the faith through which we are saved by grace is God’s gift. God saving us by grace through faith is God’s gift. It is why we can call salvation a gift, and it is why we can call faith a gift. God gifts us faith.
It is all pure gift. We are the passive recipients of God’s gracious work to save us through faith.
John 1:13 – Being born of God is a result of belief, not a prerequisite to it
This is an Ordo Salutis question. I would agree that faith is not “prerequisite” to regeneration. But if by “being born of God is a result of belief” means that our regeneration is a result of God responding to our faith, i.e. I have faith, and then subsequently, God makes me born again. Then I quite disagree. Regeneneration is neither pre-faith nor post-faith; faith and regeneration are intrinsically together as one thing. To have faith is to be born again; to be born again is to have faith. Faith does not precede regeneration; and regeneration does not precede faith. When God makes us new by the Spirit, that means we are a new man, to have faith. One cannot have faith without being born again; and one cannot be born again without faith.
As such we are not made new by the power of our own will and ability, but of God’s grace. And that being made new means that where we did not believe, we now believe. And this by the grace, kindness, and love of God who meets us in Word and Sacrament. Because that is what grace is; God coming down. That’s the Incarnation, that’s the Cross, that’s Baptism, that’s the Lord’s Supper, that’s God’s word: that’s the Gospel. God comes down, we don’t go up.
Nowhere does Scripture teach that spiritual beings (or humans) are ontologically incapable of trusting God. Rather, they refuse to do so. This is why so many calls in Scripture appeal to the will: “Choose this day whom you will serve” (Joshua 24:15), “Seek the Lord while He may be found” (Isaiah 55:6), “You refuse to come to Me that you may have life” (John 5:40). These are not rhetorical performances—they are genuine invitations requiring human response.
To whom is said “Choose this day whom you will serve”, to whom is said “Seek the the LORD while He may be found”? To Israel, correct? Though you are absolutely correct to say that we refuse to believe, we refuse to obey. And that’s the problem. We are, in our sin, wholly and entirely sinful, at enmity toward God. We do not seek God, we do not love God. We have entered into this world sinful beyond measure, rebellious, born in death and sin and enemies of God. Our total inability to choose God, to love God, to be obedient to God, and turn toward God is because we are, wholly and entirely, sinful. Sinful beyond measure.
This cannot be explained in a purely monergistic framework without undermining the plain narrative Jesus gives.
The seed is sown. Sometimes there is external factors–birds of the air for example. But at no point does the ground itself do something itself–the seed of the word takes root unless plucked by birds, choked out by thistles, or baked in the sun, etc. It is the activity of rejection that results in non-productivity for the seed.
Rejecting the Gospel is very much the work of the fallen and sinful human will. But faith is the work of God.
As we start moving toward quoting the ancient and holy fathers of the Church. What we are soon discovering is that each of us is likely to find fathers and their statements with which we agree, and fathers and statements with which we disagree. I would, for example, argue that the concern of Justin, Origen, and others is firmly within the category of rejecting Pagan fatalism. That is their concern, that is the context. The particular theological issues which Augustine is dealing with has moved away from Paganism, and is now a firmly internal matter of Christian theology, at least in part brought about because of the Pelagian Controversy. As such St. Augustine is defending the faith from heresy; Justin and Origen are rejecting Paganism.