Genesis 49:3

My strength, &c. He calls him his strength, as being born whilst his father was in his full strength and vigour; he calls him the beginning of his sorrow, because cares and sorrows usually come on with the birth of children. --- Excelling in gifts, &c., because the first-born had a title to a double portion, and to have the command over his brethren, which Ruben forfeited by his sin; being poured out as water; that is, spilt and lost. (Challoner) --- In command. He ought to have succeeded to his father in authority. But Joseph entered in upon his rejection, 1 Paralipomenon v. 1. The priesthood was given to Levi's descendants; and the regal power, partly to those of Joseph, who reigned over the ten tribes, for a long time; and partly to the posterity of Juda, who exercised dominion over all the people of Israel. (Chaldee) (Worthington)