Genesis says the dying Jacob took the firstborn's double share from Reuben and gave it to Joseph's sons, putting the younger first

Genesis 48 says that when Jacob lay ill in Egypt, Joseph brought his two sons, Manasseh, the elder, and Ephraim. Jacob claimed them as his own: they would be his "as Reuben and Simeon," his two eldest. Joseph placed Manasseh at Jacob's right hand. Jacob crossed his arms and put his right hand on the younger Ephraim. Joseph objected. Jacob refused and said Ephraim would be the greater. He also gave Joseph "one portion above thy brethren." In Genesis 49 Jacob addressed each son. To Reuben he said: you are my firstborn, "unstable as water," you shall not excel, because you went up to your father's bed. He cursed the anger of Simeon and Levi and said they would be scattered. To Judah he said the sceptre would not depart from him. Then he asked to be buried in the cave of Machpelah, drew his feet into the bed and died. The book of Chronicles states the result: Reuben's birthright "was given unto the sons of Joseph," while "Judah prevailed above his brethren, and of him came he that is the prince." Joseph's line received two tribes, Ephraim and Manasseh. The genealogy at the end of Ruth runs from Judah's son Perez to King David. The Jewish Encyclopedia notes that in early times the father's will fixed the chief heir's share, before Deuteronomy required a double portion for the firstborn. Genesis 50 says Jacob's sons carried him to Canaan and buried him at Machpelah.