So the child grew and was weaned. And Abraham made a great feast on the same day that Isaac was weaned. And Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, mocking.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.”Genesis 21:8-10
But, as he who was born according to the flesh then persecuted him who was born according to the Spirit, even so it is now. Nevertheless what does the Scripture say? “Cast out the bondwoman and her son, for the son of the bondwoman shall not be heir with the son of the freewoman.”Galatians 4:29-30.
Those verses did mention :
1. Sarah’s mistreatment of Hagar
2. Isaac being the heir of God’s promises to Abraham
Nothing in those verses mentions enmity or bad blood between the two half siblings during their lifetimes.