The son born according to the flesh is Ishmael. The son born according to promise is Isaac. According to Genesis 21:9, Ishmael ridiculed and mocked Isaac. Paul refers to this incident and says that it is an example of a pattern that has continued since that day.1 The children of the slave (the Judaizers/Jews) focus on the works of the flesh and they resist those who are born of the Spirit, namely the children of the free (Christians). With their insistence on the need for Gentile believers to be circumcised and submit to the old covenant law, the Judaizers are in effect persecuting the Galatian believers.2
29 et de même qu'alors celui qui était né selon la chair persécutait celui qui était né selon l'Esprit, ainsi en est-il encore maintenant.