(Devarim 33:20) "And of Gad he said, etc.": Why is this written? Because it is written (Bereshith 47:2) "And from the 'edge' of his brothers he (Joseph) took five men and presented them to Pharaoh," here it is specified that he took them from those whose names were doubled, and Gad was one of them.
Pharaoh — Joseph and the Lawgiver
Sifrei Devarim 355:1