Rashi on Deuteronomy 33:7/רש"י על דברים ל״ג:ז׳

1וזאת ליהודה AND THIS IS FOR JUDAH — He mentioned Judah immediately after Reuben because both of them made confession of the wrong that was theirs, as it is said, (Job 15:18-15:19) “Because wise men have told their sins … unto them alone [the land was given] and no stranger passed amidst them”. Further our Rabbis explained that during the whole forty years that Israel was in the wilderness Judah's bones were moving about in his coffin because of the excommunication that he had invoked upon himself, as it is stated that he said "If I do not bring him unto thee … I shall be sinning against my father all days" (cf. Rashi thereon: “also in the world to come”). Moses said, “Who brought it about that Reuben confessed his sin?” Judah, etc. (Sotah 7b; Bava Kamma 92a).

2שמע ה' קול יהודה HEAR, O LORD, THE VOICE OF JUDAH — Hear the prayer of Judah’s descendants, David and Solomon, and of Asa because of the Ethiopians, of Jehoshaphat because of the Ammonites and of Hezekiah because of Sannecherib (cf. Sifrei Devarim 348:8),

3ואל עמו תביאנו AND BRING HIM TO HIS PEOPLE in peace from battle;

4ידיו רב לו LET HIS HANDS רב FOR HIM — let them successfully strive for him (רב) and avenge his wrongs,

5ועזר מצריו תהיה AND BE THOU A HELP TO HIM FROM HIS ADVERSARIES — He here prayed for Jehoshaphat with regard to the battle at Ramoth Gilead, as it states, (II Chronicles 18:31) “And Jehoshaphat cried and the Lord helped him”. — Another explanation of שמע ה' קול יהודה HEAR, O LORD, THE VOICE OF JUDAH — Here in Judah’s blessings he alluded to Simeon (שמע) (i.e., Simeon’s blessing was included in that of Judah). And indeed, when they divided the land of Israel amongst the tribes, Simeon took his portion from amongst Judah’s lot, as it is said, (Joshua 19:9) “Out of the allotment of the children of Judah was the inheritance of the children of Simeon” (cf. Sifrei Devarim 348:5). {And why did he not assign to him (to Simeon) a separate blessing? Because he had something in his heart against him on account of what he had done at Shittim (Numbers 25:14). thus is it written in the Agada on the Psalms}.