Aquinas’ Retroactive New Covenant

I have previously shown at length how very similar Augustine’s understanding of the New and Old Covenants is to 1689 Federalism. He limits the Old Covenant to temporal, earthly promises and argues that OT saints were saved by the New Covenant.

[T]he happy persons, who even in that early age [the Old Testament] were by the grace of God taught to understand the distinction now set forth, were thereby made the children of promise, and were accounted in the secret purpose of God as heirs of the New Testament; although they continued with perfect fitness to administer the Old Testament to the ancient people of God

Augustine: Proto-1689 Federalist

Aquinas followed Augustine on this point, citing him several times in Summa Theologica I-II, 106-107 (Old “Law” = Old Covenant; New “Law” = New Covenant).

[T]he Old Law, which was given to men who were imperfect, that is, who had not yet received spiritual grace, was called the “law of fear,” inasmuch as it induced men to observe its commandments by threatening them with penalties; and is spoken of as containing temporal promises…

the New Law which derives its pre-eminence from the spiritual grace instilled into our hearts, is called the “Law of love”: and it is described as containing spiritual and eternal promises…

although the Old Law contained precepts of charity, nevertheless it did not confer the Holy Ghost…

the New Law is chiefly the grace itself of the Holy Ghost, which is given to those who believe in Christ…

Nevertheless there were some in the state of the Old Testament who, having charity and the grace of the Holy Ghost, looked chiefly to spiritual and eternal promises: and in this respect they belonged to the New Law…

As to those under the Old Testament who through faith were acceptable to God, in this respect they belonged to the New Testament: for they were not justified except through faith in Christ, Who is the Author of the New Testament…

No man ever had the grace of the Holy Ghost except through faith in Christ either explicit or implicit: and by faith in Christ man belongs to the New Testament. Consequently whoever had the law of grace instilled into them belonged to the New Testament…

at all times there have been some persons belonging to the New Testament, as stated above.

The Catechism of the Catholic Church specifically quotes Aquinas on this point (1964).

There were . . . under the regimen of the Old Covenant, people who possessed the charity and grace of the Holy Spirit and longed above all for the spiritual and eternal promises by which they were associated with the New Law… [E]ven though the Old Law prescribed charity, it did not give the Holy Spirit, through whom “God’s charity has been poured into our hearts.

I mention all of this simply to re-iterate the historicity of the concept. It is not an idea invented by baptists in response to paedobaptism. It is drawn from Scripture itself and has been recognized by various traditions for a very long time.