4:28-31 The history thus explained is applied. So then, brethren, we are not children of the bond-woman, but of the free. If the privileges of all believers were so great, according to the new covenant, how absurd for the Gentile converts to be under that law, which could not deliver the unbelieving Jews from bondage or condemnation! We should not have found out this allegory in the history of Sarah and Hagar, if it had not been shown to us, yet we cannot doubt it was intended by the Holy Spirit. It is an explanation of the subject, not an argument in proof of it. The two covenants of works and grace, and legal and evangelical professors, are shadowed forth. Works and fruits brought forth in a man's own strength, are legal. But if arising from faith in Christ, they are evangelical. The first covenant spirit is of bondage unto sin and death. The second covenant spirit is of liberty and freedom; not liberty to sin, but in and unto duty. The first is a spirit of persecution; the second is a spirit of love. Let those professors look to it, who have a violent, harsh, imposing spirit, towards the people of God. Yet as Abraham turned aside to Hagar, so it is possible a believer may turn aside in some things to the covenant of works, when through unbelief and neglect of the promise he acts according to the law, in his own strength; or in a way of violence, not of love, towards the brethren. Yet it is not his way, not his spirit to do so; hence he is never at rest, till he returns to his dependence on Christ again. Let us rest our souls on the Scriptures, and by a gospel hope and cheerful obedience, show that our conversation and treasure are indeed in heaven.

29. persecuted—Ishmael "mocked" Isaac, which contained in it the germ and spirit of persecution (Ge 21:9). His mocking was probably directed against Isaac's piety and faith in God's promises. Being the older by natural birth, he haughtily prided himself above him that was born by promise: as Cain hated Abel's piety.

him … born after the Spirit—The language, though referring primarily to Isaac, born in a spiritual way (namely, by the promise or word of God, rendered by His Spirit efficient out of the course of nature, in making Sarah fruitful in old age), is so framed as especially to refer to believers justified by Gospel grace through faith, as opposed to carnal men, Judaizers, and legalists.

even so it is now—(Ga 5:11; 6:12, 17; Ac 9:29; 13:45, 49, 50; 14:1, 2, 19; 17:5, 13; 18:5, 6). The Jews persecuted Paul, not for preaching Christianity in opposition to heathenism, but for preaching it as distinct from Judaism. Except in the two cases of Philippi and Ephesus (where the persons beginning the assault were pecuniarily interested in his expulsion), he was nowhere set upon by the Gentiles, unless they were first stirred up by the Jews. The coincidence between Paul's Epistles and Luke's history (the Acts) in this respect, is plainly undesigned, and so a proof of genuineness (see Paley, Horæ Paulinæ).