A.T. Robertson Commentary Galatians 4:29

"But as then he that was born after the flesh persecuted him [that was born] after the Spirit, so also it is now." — Galatians 4:29 (ASV)

Persecuted (εδιωκεν). Imperfect active of διωκω, to pursue, to persecute. Genesis 21:9 has in Hebrew "laughing," but the LXX has "mocking." The Jewish tradition represents Ishmael as shooting arrows at Isaac.

So now (ουτος κα νυν) the Jews were persecuting Paul and all Christians (1 Thessalonians 2:15f.).