Why did Ya'akov initially refer to Yehudah as a lion cub and then, as a lion?
Rashi (citing Targum Onkelos): Because, since he was speaking about David, 1 he referred to him first at the beginning of is leadership (still in the days of Sha'ul), 2 and then, to the period after he was crowned king, when he would establish a firm grip on the throne and (like a lion and lioness in their lair), he would be invincible.
Targum Yonasan: First, he referred to the two sinful episodes 3 that had already passed for which Yehudah himself had already attained atonement, then to his leadership as a king.
Rashbam: He compared him to a lion cub, because it is both swifter and stronger than an old lion; and when he then compared him to a lion and a lioness, he was referring to after he was established and sitting safely on the throne, when the enemy no longer dared challenge him.
Seforno: He referred to Yehudah as a lion cub, since, although he did not yet have a kingdom, he ruled over his brothers, and was destined for sovereignty. He did not order Yosef's death 4 because he was like a lion crouching peacefully, as lions who caught their prey tend to do, and who do not arise to flee before any other wild animals that appear.
From which prey did Yehudah remove himself?
Rashi: From the killing of Yosef - of which Ya'akov had initially suspected him; 1 and from the killing of Tamar, when he admitted and declared "Tzadkah Mimeni!" (38:26).
Rashbam: He was referring to after David had captured the nations and settled down in Yerushalayim. 2
Hadar Zekenim: Hashem saved David from a lion and a bear. Due to this, he fought Galyus and rose.
Riva: It was [only] from killing Tamar.
What is the connection between the first half of the Pasuk and the second half?
Rashi #1: Refer to 49:9:1:1.
Targum Yonasan: Refer to 49:9:1:2.
Rashi 2: It was because Yehudah displayed that great strength of character (refer to 49:9:2:1) that he earned the merit for his grandson Sh'lomoh to dwell peacefully in Eretz Yisrael, 1 like a lion and lioness in their lair. 2
רש"י: ממה שחשדתיך וכו': למה יעקב חשד דוקא ביהודה?
גור אריה: יהודה היה מלך ולכן היה לו להתיירא ממלכות יוסף.