The child grew and was weaned, and on the day Isaac was weaned Abraham held a great feast. But Sarah saw that the son whom Hagar the Egyptian had borne to Abraham was mocking, and she said to Abraham, “Get rid of that slave woman and her son, for that slave woman’s son will never share in the inheritance with my son Isaac.”
The matter distressed Abraham greatly because it concerned his son. But God said to him, “Do not be so distressed about the boy and your maidservant. Listen to whatever Sarah tells you, because it is through Isaac that your offspring will be reckoned. I will make the son of the maidservant into a nation also, because he is your offspring.”
Early the next morning Abraham took some food and a skin of water and gave them to Hagar. He set them on her shoulders and then sent her off with the boy. She went on her way and wandered in the desert of Beersheba. Genesis 21:8-14

God knew that there would be no peace between the mothers (Sarah and Hagar) and the sons (Isaac and Ishmael). Maybe, Ishmael’s or Isaac’s life would be threatened. If Isaac had died, no Savior would be born into the world. As history shows, the two lineages were at odds with one another and still are today. God needed to remove the possibility of murder.

Abraham only took them out into the desert when God promised to take care of them. This was a pretty secure guarantee. The desert wasn’t a place of abandonment but an invitation to freedom for Hagar and Ishmael to have their own lives.

Even though they were not part of God’s promise to Abraham, God still protected them.

The lineage that came from Ishmael were desert dwellers, living in and near Egypt. The fact that they are archers, made them a dangerous enemy. God even loves the enemy before they became His enemies.