Genesis 48:5

48:5 “Now, as for your two sons, who were born to you in the land of Egypt before I came to you in Egypt, they will be mine. Ephraim and Manasseh will be mine just as Reuben and Simeon are.

Genesis 48:13-14

48:13 Joseph positioned them; he put Ephraim on his right hand across from Israel’s left hand, and Manasseh on his left hand across from Israel’s right hand. Then Joseph brought them closer to his father. 48:14 Israel stretched out his right hand and placed it on Ephraim’s head, although he was the younger. Crossing his hands, he put his left hand on Manasseh’s head, for Manasseh was the firstborn.

Genesis 48:18-20

48:18 Joseph said to his father, “Not so, my father, for this is the firstborn. Put your right hand on his head.”

48:19 But his father refused and said, “I know, my son, I know. He too will become a nation and he too will become great. In spite of this, his younger brother will be even greater and his descendants will become a multitude of nations.” 48:20 So he blessed them that day, saying,

“By you will Israel bless, saying,

‘May God make you like Ephraim and Manasseh.’”

So he put Ephraim before Manasseh.

Deuteronomy 33:17

33:17 May the firstborn of his bull bring him honor,

and may his horns be those of a wild ox;

with them may he gore all peoples,

all the far reaches of the earth.

They are the ten thousands of Ephraim,

and they are the thousands of Manasseh.