NT believers.

John Calvin has written:

“In the same passage, Augustine, with great shrewdness, remarks, that from the beginning of the world the sons of promise, the divinely regenerated, who, through faith working by love, obeyed the commandments, belonged to the New Testament; entertaining the hope not of carnal, earthly, temporal, but spiritual, heavenly, and eternal blessings, believing especially in a mediator, by whom they doubted not both that the Spirit was administered to them, enabling them to do good, and pardon imparted as often as they sinned. The thing which he thus intended to assert was, that all the saints mentioned in scripture, from the beginning of the world as having been especially selected by God, were equally with us partakers of the blessing of eternal salvation.”

(Calvin, John. Institutes of the Christian Religion, Grand Rapids, MI: Wm. B. Eerdmans Publishing, 1998, p. 395.)