Genesis 27:15

27:15 Then Rebekah took her older son Esau’s best clothes, which she had with her in the house, and put them on her younger son Jacob.

Genesis 29:26

29:26 “It is not our custom here,” Laban replied, “to give the younger daughter in marriage before the firstborn.

Genesis 43:33

43:33 They sat before him, arranged by order of birth, beginning with the firstborn and ending with the youngest. The men looked at each other in astonishment.

Genesis 49:3

49:3 Reuben, you are my firstborn,

my might and the beginning of my strength,

outstanding in dignity, outstanding in power.