Bereschit 49:9 Kommentar: Rashi, Rashbam, Sforno & Or HaChaim

גור אריה A YOUNG LION — He prophesied this with reference to David who, when he began his military career, was but as a whelp — as it states, (2 Samuel 5:2) “when Saul was king over us it was thou that didst lead out and bring in Israel” — but who later on became as a lion when they made him king over themselves. That is what Onkelos means by translating it “A ruler he shall he בשרויא” — at the beginning

גור אריה יהודה, an expression similar to כפיר אריות, (Judges 14,5) the young, not fully grown lion is called גור, whereas the fully mature lion is known as כפיר as we know from Ezekiel 19,2 בתוך כפירים רבתה גוריה, “a young lioness crouched among the fully grown lions.” The young lion enjoys the advantage of speed and self-confidence, hence more aggressiveness, over an aging lion. It is not surprising therefore that when complimenting Yehudah, Yaakov compares him to a young lion rather than to a fully mature one who is already on the way to decline.

גור אריה יהודה, although Yehudah is not a fully grown lion, i.e. not enjoying the trappings of royalty, possessing a land, etc, he is at least comparable to a lion cub, preeminent among his brothers. In the future he will rule as king in the full meaning of the word. All this, in spite of the fact that