Therefore she said to Abraham, “Cast out this bondwoman and her son; for the son of this bondwoman shall not be heir with my son, namely with Isaac.” And the matter was very displeasing in Abraham’s sight because of his son. (Gen 21,10-11)

At first overwhelming joy, but then great sorrow... Until Isaac came, the camp was quiet, so it was quite clear who could afford what and how the roles were divided. But now Abraham was "greatly troubled". If he had to part with something obviously evil, he surely would not have worried or regretted it. Like any man, he would probably have had difficulty seeing and acknowledging it at first, but after he had come to that conclusion, he would have taken the expulsion of the evil thing as a relief.

But the problem called Ishmael, in short, was that it was not evil, quite the contrary. After all, he was his own son! From the time of his birth, he saw him as the chief heir to the whole farm and house, because from his point of view, God was not fulfilling His ancient promise. But now everything was turned upside down. God had come and confirmed that what He had said had always been true, and it had never changed. Abraham wondered how many times this God had actually surprised him...

Now there was clearly no avoiding it. Isaac would be in permanent danger from his older brother, Ishmael was only 13 years old now, but he was already showing hostility, and the claim to the inheritance could escalate into a mortal dispute at any time. It was clear that Hagar and Ishmael saw things differently than that they should be put on the back burner for good. The descent from glory was extremely humbling for them, and so they were left with one last hope: Abraham's apparent weakness for his firstborn son. Sarah, sensing this, took the initiative and urged her husband: you must resolve this as soon as possible, while you still have strength enough. Ishmael must go.

Until Isaac came, the situation in the camp was "stable". However, the arrival of a purely heavenly seed in an environment already accustomed to half-heartedness will bring about a major crisis. The same is true in Scripture of every mixture of the holy and the unholy as practiced by Israel for centuries, and by the church after its decline into lukewarmness. The Word will come and bring unrest, a separation of the holy from the unholy (or from what is holy only in outward appearance). And the same is true in the life of every man as he wages the struggle for a victorious life, trying to reach it by his own strength or on the contrary by the power of the Holy Spirit.