Genesis 35:23

35:23 The sons of Leah were Reuben, Jacob’s firstborn, as well as Simeon, Levi, Judah, Issachar, and Zebulun.

Genesis 41:52

41:52 He named the second child Ephraim, saying, “Certainly God has made me fruitful in the land of my suffering.”

Genesis 46:8

46:8 These are the names of the sons of Israel who went to Egypt – Jacob and his sons:

Reuben, the firstborn of Jacob.

Genesis 49:3

49:3 Reuben, you are my firstborn,

my might and the beginning of my strength,

outstanding in dignity, outstanding in power.