When Joseph was enslaved in Egypt, he eventually rose to power and married an Egyptian woman named Asenath. Two children resulted from this marriage and they were Ephraim and Manasseh.
“And the name of the second called he Ephraim: For God hath caused me to be fruitful in the land of my affliction.” – 41:52
During the blessing ceremony, Joseph places them before Jacob, and Jacob adopts both boys as his own children, thus making them “tribes” of Israel.
“And now thy two sons, Ephraim and Manasseh, which were born unto thee in the land of Egypt before I came unto thee into Egypt, are mine; as Reuben and Simeon, they shall be mine.” – 48:5
During the ceremony, Jacob blesses both boys, but he places Ephraim before Manasseh, even though he was the youngest and Joseph objected.
“And when Joseph saw that his father laid his right hand upon the head of Ephraim, it displeased him: and he held up his father’s hand, to remove it from Ephraim‘s head unto Manasseh’s head. And Joseph said unto his father, Not so, my father: for this is the firstborn; put thy right hand upon his head. And his father refused, and said, I know it, my son, I know it: he also shall become a people, and he also shall be great: but truly his younger brother shall be greater than he, and his seed shall become a multitude of nations.” – Genesis 48:17-19
It isn’t until later that we find out that the ceremony was actually the passing of the birthright from Reuben to the sons of Joseph.
“Now the sons of Reuben the firstborn of Israel, (for he was the firstborn; but, forasmuch as he defiled his father’s bed, his birthright was given unto the sons of Joseph the son of Israel: and the genealogy is not to be reckoned after the birthright. For Judah prevailed above his brethren, and of him came the chief ruler; but the birthright was Joseph’s:)” – 1 Chronicles 5:1-2
Why The Birthright Is Important
The birthright was usually passed from father to the eldest son, essentially making him the “man of the house” after the passing of the father. The oldest son would have all rights to the money, land, slaves, etc.
This status was usually assumed by the eldest son unless the father intentionally passed it onto someone else, such as what happened with Ephraim and Manasseh.
Because of this ceremony, it is the half Egyptian tribes of Ephraim and Manasseh that gained all the rights of the father after the passing of Jacob.