Genesis 49:8

But, one may say, why did it seem right to the prophet to impose on Judah such a blessing, when he had done nothing like that for the first ones?Now learn the reason.… In fact David had to be born from the tribe of Judah and Christ from David with regard to the flesh. [Therefore] the prophet foreknowing the future events in their spiritual sense has blessed there David, who descended from Judah, and the Christ who, according to the flesh, had to be born from David, so that he might receive from God not only the blessing according to the spirit but also the blessing according to the flesh.

Who are the brothers who praised and adored him but the apostles, to whom the Lord said, "Are you my brothers and coheirs?" And then to say, "Your hands are on the back of your enemies" can mean either of two things: by simply stretching his hands [on the cross] Christ was able, in the course of the fight against his enemies, to triumph over [invisible] powers. Or he has become the Lord and Master and Judge of all those who were his enemies according to the flesh, after being set in this role by the Father.

(Verse 8.) Judah, your brothers will praise you. Because Judah, confession or praise, is subsequently written: Judah, your brothers will confess to you: or, your brothers will praise you.

This can be referred to the historical Judah as well as to those kings who were his descendants. They broke the back of their enemies by administering the kingdom of that people. But this can also be fittingly referred to Christ, who is praised with good reason by his brothers, that is, by the apostles whom he himself called brothers in the Gospel. And his enemies, on whose back is his hand, appear to be those whom the Father promised to place under his feet by saying, "Sit at my right hand until I place your enemies under your feet." They are enemies as long as they are unbelieving and unfaithful, and for that reason they are struck on the back. But after their conversion they become brothers and praise the One who, by summoning them to the adoption of the Father, has made them his coheirs and brothers. It is said correctly that the back of the enemies is struck by Christ. All those who worshiped the idols turned their back to God, as the Lord, through the prophet, accused them by saying, "They turned their backs to me, and not their faces." Therefore he strikes their back so that after being converted they may turn their back to the idols and raise their forehead to God and may accomplish what is written here: "Your father's sons shall bow down before you." In fact, they adore him when they have become sons of the Father and have received the spirit of adoption in which they cry out, "Abba, Father." No one calls Jesus Christ Lord except those who are in the Holy Spirit.

In these blessings, the way that they expressly introduced the listeners to the prophecy concerning the incarnation of our Savior is extremely clear. At the beginning of the blessing the meaning of the name itself is set before the reader's eyes, and also the fact that the tribe of Judah was superior to all the others for its glory. If one wants to interpret the name Judah, it means "praise" or "hymn" or "celebrated with hymns." These words therefore must be referred to Christ, who obviously is from the tribe of Judah according to the flesh. He was born from Judah, Jesse and David and from that virgin who was assumed for the generation of the flesh.… You must be praised, and to God you will give back the glory that is due him. No one else is suited to be glorified but only the living and well-known God. Even though you appeared human and emptied yourself, you are known to be holy and eternal. Your brothers according to human nature will not be related to you as man but rather will praise you as Lord, though placed among your brothers, and will glorify you as Creator, though you have placed yourself with them among the creatures. They will recognize you as the Lord and the King, even though you appeared veiled under the "form of a slave." Moreover, he foretold the fact that the Immanuel would have overcome all those who opposed him … saying, "Your hands on the back of your enemies." And Christ himself, through the voice of David, foretold the same thing. He said, "I will pursue my enemies and will take them, and I will not return until they are defeated. I will crush them, and they will not be able to stand but will fall under my feet." Then Jacob said rightly, "His hands will be on the back of his enemies," that is, as those of the one pursuing rather than those of one fleeing, as those of the one striking rather than those of one who is struck.