Augustine of Hippo : Paul means those who are truly prepared for the vision of God. These are distinguished from those who are called by this name [Israel] and in their carnal blindness refuse to see the Lord, spurning his grace, still desiring to be enslaved by temporal things. — EPISTLE TO THE Galatians 63 [1B.6.15-16] Jerome : (Verse 16.) And whoever follows this rule, peace and mercy be upon them, and upon the Israel of God. All things are directed according to the standard; and whether they be right or wrong, when the rule is applied, they are judged. So too the teaching of God is like a standard of speech, which judges between what is just and unjust: whoever follows it will have peace within themselves that surpasses all understanding; and after peace, mercy, which is foremost in the Israel of God. But the true Israel is called, in distinction from those who ceased to be God's Israel. For they say they are Jews, and they are not; but they lie, being of the synagogue of Satan. And do not be surprised, if, in imitation of spiritual Israel, carnal Israel neither has peace nor mercy, of whom it is also written to the Corinthians: See Israel according to the flesh (I Cor. X, 18); since also in imitation of God and the Lord, there are many gods and many lords, whether in heaven or on earth. Beautifully, however, in one discourse, in order to conclude the letter according to the proposed argument, he called Israel the people of God; so that all the things that have been said above, not apart from the cause, but from the cause debated, may be taught. — Commentary on Galatians Oecumenius : "And those who will walk by this rule." He says, "May those who are satisfied with this rule and this teaching regard everything as a new creation, and not subject themselves to the law." "and upon the Israel of God." Israel is a faithful people, as if devoted to God. And whoever has been unfaithful, even if he descends from Jacob, is cast out from the kinship that is toward him. — Commentary on Galatians