The mockery

Abraham and Sarah didn't have perfect faith. They were promised an child in their old age but they didn't trust in God.
Abraham had a child from another woman. Hagar was the woman. Her son was called Ishmael.  This caused many issues in the house of Abraham.
Ishmael was mocking Issac. Issac was in the line of the Messiah and Ishmael wasn't.
The Bible explains that God's righteousness can't be in our sins.
If a person wants to have Jesus then that person needs to love God's righteousness.

Genesis 21:8-10

 ⁸ The child grew and was weaned, and on the day Isaac was weaned Abraham held a great feast. ⁹ But Sarah saw that the son whom Hagar the Egyptian had borne to Abraham was mocking, ¹⁰ and she said to Abraham, “Get rid of that slave woman and her son, for that woman’s son will never share in the inheritance with my son Isaac.”