Galatians 4:29

ἀλλʼ. In contrast to what we might have expected as God’s chosen, Why wonder at persecution? Isaac had to bear it at Ishmael’s hands. It should be observed that by this further evidence of the applicability of the narrative to present circumstances St Paul justifies afresh his interpretation of the identification of Isaac with believers, and Ishmael with unbelieving Jews.

ὁ κατὰ σάρκα γεννηθεὶς. Cf. Galatians 4:23.

ἐδίωκε. In those far-off days. The word but slightly exaggerates the meaning of the Hebrew tzaḥaq “mocking.” An old Rabbinic exposition (A.D. 90–120, in Gen. R. Parasha 53 on Genesis 21:9) says that Ishmael pretended to play, but shot at Isaac with a bow and arrow, really intending to kill him; illustrating this meaning of tzaḥaq from the similar word saḥaq in 2 Samuel 2:14 (see Zahn).

τὸν κατὰ πνεῦμα. For the special help of God is implied in the circumstances of Isaac’s birth, cf. Romans 4:17-21.