At that time the son born according to the flesh persecuted the son born by the power of the Spirit. It is the same now. Galatians 4:29
The “son born according to the flesh” was Ishmael. Abraham and Sarah connived to have a son rather than having faith in God’s ability to fulfil his promises. The “son born by the power of the Spirit” was Isaac. Abraham and Sarah were well beyond the age of having children naturally so God by his Spirit supernaturally enable Sarah to conceive.
Yet despite Isaac’s miraculous birth (or perhaps because of it), Ishmael persecuted him. Paul doesn’t tell us the nature of the persecution but we read this in the original account, “But Sarah saw that the son whom Hagar the Egyptian had borne to Abraham was mocking” (Genesis 21:9). Even this doesn’t give us all the details. What was he mocking Isaac about? It bothered Sarah sufficiently to ask Abraham to send Hagar and Ishmael away, which he did.
However, the most surprising conclusion to this verse is, “It is the same now.” If we live by the power of the Spirit we will be persecuted by those who do things based on their own efforts. We will be mocked by those who aren’t familiar with the ways of the Spirit.
Some days we may be the cause of persecution, when we mock the possibility that God may supernaturally intervene, when we don’t support the “Abrahams” in our lives (that is, our leaders), and when we don’t have faith in God to fulfil his promises in the face of barren circumstances.
The challenge is to live by “the power of the Spirit” and have faith in God’s ability to bring about the miraculous.