Genesis 48:19-20

But his father wouldn’t do it. He said, “I know, my son; but I know what I’m doing. He also will develop into a people, and he also will be great. But his younger brother will be even greater and his descendants will enrich nations.” Then he blessed them both: Israel will use your names to give blessings: May God make you like Ephraim and Manasseh. In that he made it explicit: he put Ephraim ahead of Manasseh.