Genesis 48:19
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. 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 48:19 belongs to the history of Joseph as ruler in Egypt during the seven years of dearth, when ten of Jacob's sons came from Canaan to buy grain and bowed down before him with their faces to the earth without recognizing him, fulfilling his earlier dreams. It belongs also to the account of the customary Jewish way for a father to bless his children by reverently laying his hands upon their heads. That laying on of hands in blessing meant asking God to bestow His blessing upon them.
The laying on of hands upon Paul and Barnabas by the ministers at Antioch carried that same meaning, as an appeal for God to bless them in devotion and dedication to the particular work He had chosen for them to do.