Genesis 29:26
29:26 “It is not our custom here,” Laban replied, “to give the younger daughter in marriage before the firstborn.
Genesis 35:23
35:23 The sons of Leah were Reuben, Jacob’s firstborn, as well as Simeon, Levi, Judah, Issachar, and Zebulun.
Genesis 38:7
38:7 But Er, Judah’s firstborn, was evil in the Lord’s sight, so the Lord killed him.
Genesis 49:3
49:3 Reuben, you are my firstborn,
my might and the beginning of my strength,
outstanding in dignity, outstanding in power.