Summary: When faith fails, then flesh takes over.
ISAAC AND ISHMAEL
1. The History
The history of Ishmael and Isaac is the history of the struggle between flesh and spirit, between the carnal seed and the spiritual seed, between the world's way and God's way.
In the first place, Abraham had faith. The LORD pointed him towards the stars, and told him “so shall your seed be.” Abraham believed in the LORD, and He counted it to him as righteousness (Genesis 15:5-6). In other words, Abraham began in faith, just as Paul had already been at pains to describe in Galatians 3:6-9.
Then faith failed, and Sarah and Abraham let the flesh take over. After all, they argued, Sarah was barren. According to the custom of the world around them, Sarah gave her handmaid to Abraham to bear seed in her name (Genesis 16:1-3).
Almost immediately Sarah regretted her rashness, and strife broke out within the family (Genesis 16:4-6). Hagar gave birth to a wild man (Genesis 16:11-12), and God's promise was put on hold for another thirteen years (Genesis 16:16-17:1).
When we look only at the physical and stop operating in the Spirit then we are bringing trouble upon ourselves. Having begun in the Spirit, are we going to be as foolish as Abraham and Sarah then were, by trying to continue in the flesh (Galatians 3:3)?
After thirteen years, the LORD again appeared to Abraham. As if to say, enough is enough: your way has only brought strife, now let's try My way. Sarah was old and barren when I told you that you were going to have a son, and now she is ancient. Yet, just so you know this is the voice of God and not some dream of your own, it is by Sarah that you are going to have the promised seed (Genesis 17:15-16). Laugh if you like, but miracle births do happen!
Ishmael grew up to despise his half-brother (Genesis 21:9), and so began the historical and on-going contention between the sons of Hagar, and the seed of Sarah, between the Arabians and Israel.
Yet there is another way in which the promised seed of Abraham is fulfilled. It is fulfilled in one who was “despised and rejected of men” (Isaiah 53:3), in a physical descendant of Isaac called Jesus (Galatians 3:16). This same Jesus is the one whose birth is celebrated by many churches on 25th of December each year – yet He is often celebrated by the world in a most unseemly manner. Or He is not celebrated at all, but shunned and scorned.
Abraham's spiritual seed is continued in another despised race: in all who are found in Christ (Galatians 3:29).
2. The Allegory
Strictly speaking, we should accept Scripture at face value before entering into the realm of allegory. The Jewish Rabbinical Schools, and no doubt the Judaisers in Galatia, were fond of allegories, as were the early church fathers. Yet it is a landscape full of potential pitfalls.
It is better for us to read Biblical history first and foremost as history, and prophecy as being applicable primarily to the situation to which it was addressed. It is more important to know “what saith the Scripture” than what the theologians, scholars, scholastics, doctors, professors and masters of divinity have to say about the Scripture. This does not, however, take away from Paul's inspiration when he likened Ishmael to law, bondage, and Judaism; and Isaac to promise, freedom and Christianity.