Genesis 21:10

Wherefore she said unto Abraham, Cast out this bondwoman and her son: for the son of this  bondwoman shall not be heir with my son, [even] with Isaac.

(Geneva Bible) - Wherefore she said unto Abraham, (*) Cast out this bondwoman and her son, for the son of this bondwoman shall not be heir with my son Isaac.
(*) Galatians 4:30 .

Genesis 15:4

And, behold, the word of the LORD [came] unto him, saying, This shall not be thine heir; but he that shall come forth out of thine own bowels shall be thine heir.

Genesis 15:3

And Abram said, Behold, to me thou hast given no seed: and, lo, one [a son of my house, a servant] born in my house is mine heir.