Deuteronomy 33:7

And this is the benediction of the tribe of Jehudah, conjoined with the portion and benediction of his brother Shemeon; and thus he spake: Receive, O Lord, the prayer of Jehudah when he goeth forth unto war, and bring Thou him back from war unto his people in peace. Let his hand take vengeance on his enemies, and be Thou his help and support against his foes.

This for Yehudah The same was said for Y e hudah — that he should live, and not die. Then he proceeded to add Hear, O God , the voice of Yehudah (when embarking in battle — since Y e hudah marched at the head of the army)

and bring him to his people (this either refers to the headquarters at Gilgal [Joshua 10: 43], or it is a prayer for those who go off to do battle in enemy territory).

his hands shall satisfy [Hebrew: rav] him i.e., his own hands shall suffice him: He shall not be in need of help from anyone, save that of God alone. But there are some who derive the word from “strife” [Hebrew: merivah], meaning that his hands will strive for him. Others relate the word to “He shot out [Hebrew: rav] lightnings” [Psalms 18: 15], along the lines of “shot at him [Hebrew: robbu]” [Genesis 49: 23].

AND THIS FOR JUDAH. “And for Judah he said likewise that he live and not die, and further added for him, hear, Eternal, the voice of Judah.” This is the opinion of Rabbi Abraham ibn Ezra. But this is not correct in accordance with our interpretation [above on the blessing of Reuben], for Judah was not involved in this [punishment of] extinction [making it necessary for] Moses to pray for him, just as he did not mention this in the blessing of the remaining tribes. But the verse is to be understood in its plain meaning: “and this is the blessing for Judah.” And by way of the Truth, [the mystic teachings of the Cabala], he singled out the attribute of zoth (this) for Judah because his is the conduct of war and from him shall be royalty forever, this being the help against his adversaries. This is the secret of the verse stating, To teach the sons of Judah the bow. Behold, it is written in the Book of Jashar, for this is the bow which is seen in the cloud concerning which it is said, ‘Zoth’ (this) is the token of the covenant.

HEAR, ETERNAL, THE VOICE OF JUDAH. He prayed for him when he goes out to fight, for it was Judah who was first to go up to fight and of him came he that is the prince to fight the enemies of Israel. And so also did Jacob say, thy hand shall be on the neck of thine enemies., 49:8.

AND BRING HIM IN INTO HIS PEOPLE — that he should return [from the fighting] in peace. HIS HANDS SHALL ‘RAV’ FOR HIM. His hands shall “be sufficient” for him, so that he need no other help except for the help of G-d Who will answer him when he prays, all as written in the words of Onkelos. So also is the opinion of the commentators.
In my opinion he [Moses] further alludes to Judah’s first war against the Canaanite concerning which G-d said, Judah shall go up first. And he states his hands shall ‘rav’ meaning that he will annex and conquer from his foes “many” lands, more than are due him as his inheritance. He intimates that Judah will give part of his inheritance to his brother Simeon, this being what is stated, Out of the allotment of the children of Judah was the inheritance of the children of Simeon, for the portion of Judah was too much for them; therefore the children of Simeon had inheritance in the midst of their inheritance. Thus Moses mentioned Simeon by allusion together with Judah.

וזאת ליהודה, this is also what I request and pray for on behalf of the people residing in the tribal territory of Yehudah that includes the members of the tribe of Shimon who were an enclave within the tribal territory of Yehudah. Let them not die in the wars in which they will be involved. They all go out to war together.

ויאמר שמע ה' קול יהודה, in addition to what Moses had said under the heading of וזאת ליהודה, that whenever this tribe would pray to G’d either during war or any other occasion

ידיו רב לו ועזר מצריו תהיה, though his own hands strive for him (during battle), help him against his foes.” I pray that You, G’d, be his hands, although to all intents and purposes people watching him may credit his own prowess with his victory.” רב לו, an expression of avenging wrong done to him. עזר מצריו, when they are attacking him and he is on the defensive.

וזאת ליהודה, “”and this for Yehudah;” i.e. “and this is the blessing for Yehudah. Moses means that the blessing he had just given to Reuven will also apply to Yehudah. He prayed that they both be extraordinarily successful in that war. The reason he also singled out Yehudah for such a blessing was that that tribe usually was always at the head of the army. (Compare Judges 1,2) In that verse G–d had answered t]he people’s query who should lead them in war now that Joshua had died. Our sages in the Talmud, tractate Sotah folio 7 state that the bones of Yehudah were rattling in their coffin all the years that the Israelites wandered in the desert, the reason being that he had said to his father Yaakov before obtaining permission to take Binyamin to Egypt, that he would consider himself as having sinned unforgivably against him for all his life if he did not bring him back safe and sound. (Genesis 43,9). Even though it appears at first glance as if Binyamin had descended with the rest of Yaakov’s family (Genesis 46,21) when a wise man utters a curse, even a conditional one, it comes true at some time [Yaakov had cursed the anonymous person who had stolen Lavan’s t’raphim if he would be found, and although he never found that person Rachel died prematurely on account of that as she had stolen them. Ed.] (compare Talmud, tractate Makkot, folio 11) The Talmud there describes that at the time when David dug the hole known as shitin, under the site where the Temple would stand in the future, the subterranean waters started rising from the depths and threatened to flood the earth. At that point, when Achitofel did not rule on the subject though he had been openly invited to do so, David reasoned as follows before writing the holy name of G–d on a shard commanding the waters to stop rising. If in the case of a woman suspected of infidelity by her husband, the priest dissolves a parchment with the Holy Name of the Lord in order to help restore marital harmony, when the life of the whole of humanity is at stake, surely I am not only allowed but I have the duty to try and save mankind by that means. (Compare Numbers 5, 11-31) When Achitophel saw that his advice concerning the rebellion of Avshalom had not been followed, he went home and arranged his affairs, and hung himself. (see beginning of chapter 17). [Achitofel, according to tradition was the outstanding Torah scholar of his generation, and at one time David’s tutor. Ed.] The Talmud Makkot quoted before comes to the conclusion that Moses when wondering why the bones of Reuven did not rattle in their coffin whereas those of Yehudah, his brother did not, especially since it had been Yehudah’s public confession of having fathered Tamar’s children which had caused Reuven to also publicly confess that he had committed an indiscretion with Bilhah, and remains with a question, else he would not have commenced Yehudah’s blessing with the words he did. He did not bless Shimon, just as his father had also not given him a blessing on his deathbed, as in addition to the deceit and violence at Sh’chem, as the leader of that tribe, Zimri had added to his sin by sleeping provocatively with a Midianite princess, as reported in Numbers 25,6. Although Levi had been Shimon’s partner in the killing of the male population of Sh’chem, his descendants had rehabilitated themselves when, to a man, none of them participated in worshipping the golden calf. (Compare Exodus 32,26) Moses at least hinted at a blessing for Yehudah, according to the Talmud in Makkot there.