?u?Mikneh Rav Hayu li?Venei Re?uven ve?li?Venei Gad?. Why does the Torah mention the B?nei Re?uven first?
Ramban and R. Bachye: Because, Reuven was the son of one of Ya?akov?s main wives, whereas Gad was the son of one of his maidservents. 1
Refer to 32:1:1: & 3.