22 Because it is in the Writings, that Abraham had two sons, one by the servant-woman, and one by the free woman. 23 Now the son by the servant-woman has his birth after the flesh; but the son by the free woman has his birth through the undertaking of God. 24 Which things have a secret sense; because these women are the two agreements; one from the mountain of Sinai, giving birth to servants, which is Hagar. 25 Now this Hagar is the mountain Sinai in Arabia, and is the image of the Jerusalem which now is: which is a servant with her children. 26 But the Jerusalem on high is free, which is our mother. 27 For it is in the Writings, You who have never given birth, be glad; give cries of joy, you who have had no birth-pains; for the children of her who has been given up by her husband are more than those of the woman who has a husband. 28 Now we, brothers, as Isaac was, are the children of the undertaking of God. 29 But as in those days he who had birth after the flesh was cruel to him who had birth after the Spirit, even so it is now. 30 What then do the Writings say? Send away the servant-woman and her son; for the son of the servant-woman will not have a part in the heritage with the son of the free woman.
Matthew Henry's Commentary on Galatians 4:22-30
Commentary on Galatians 4:21-27
(Read Galatians 4:21-27)
The difference between believers who rested in Christ only, and those who trusted in the law, is explained by the histories of Isaac and Ishmael. These things are an allegory, wherein, beside the literal and historical sense of the words, the Spirit of God points out something further. Hagar and Sarah were apt emblems of the two different dispensations of the covenant. The heavenly Jerusalem, the true church from above, represented by Sarah, is in a state of freedom, and is the mother of all believers, who are born of the Holy Spirit. They were by regeneration and true faith, made a part of the true seed of Abraham, according to the promise made to him.
Commentary on Galatians 4:28-31
(Read Galatians 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.