Genesis 49 is the first place in the bible the blessing of Joseph is mentioned. Hundreds of years later, Moses added to what Jacob started. The fact Moses added to the blessing of Joseph well after Joseph had died shows the blessing of Joseph is a work in progress. The fact Moses is still adding on proves the blessing will be given to a future biblical figure who is yet to be born.
In Genesis 49, gave out blessings to his 12 sons. Just before he breathed his last, he asked to be buried in present day Samaria. The blessing he gave to his son Joseph is of particular interest. Genesis 49: 22-26 states, 22 Joseph is a fruitful bough, a fruitful bough by a well whose branches run over the wall. 23 Skilled archers have bitterly attacked and sorely worried him; they have shot at him and persecuted him. 24 But his bow remained strong and steady and rested in the Strength that does not fail him, for the arms of his hands were made strong and active by the hands of the Mighty God of Jacob, by the name of the Shepherd, the Rock of Israel. 25 By the God of you father, Who will help you, and by the Almighty, Who will bless you with blessings of the heavens above, blessings lying in the deep beneath, blessings of the breasts and of he womb. 26 The blessings of your father on you are greater tan the blessings of my forefathers on me, and are as lasting as the bounties of the eternal hills; they shall be on the head of Joseph, and on the crown of the head of him who was the consecrated one and the one separated from his brethren and the one who is prince among them.
Jacob is trying to create a dominant future leader who comes from both himself and his son Joseph. This future leader would get his authority from both God and biblical scripture.
This strategy which was started by Jacob ensures the bible has been prepared to overthrow those who attack it.