You see that here the tribe of Simeon is left out and not blessed. For what reason, who knows? That the Hebrews make the selling of Joseph and the fornication of Baal Peor the cause, means nothing to me. Jerome thinks that Judas Iscariot, who was to come from this tribe, deserved this. But let fables be fables. It is certain, however, that Simeon did not have his own lot, as did the others, but had it in the tribe of Judah (Joshua 19:1). Therefore he must be content with the general blessing which follows.
“There is none like God, O Jeshurun, who rides through the heavens to your help, and in His majesty through the skies” (v. 26); that is, through thunder He displays His majesty. “The eternal God is your dwelling place, and underneath are the everlasting arms” (v. 27); that is, although He lives in the heavens, nevertheless His arms are supreme in the world to free His own, as follows. “And He thrust out the enemy before you, and said: Destroy”; that is, He will cast him down with one word. “So Israel dwelt in safety, the foundation of Jacob alone, in a land of grain and wine” (v. 28); that is, he will delight in a fertile land. “Yea, His heavens drop down dew,” namely, to make it fruitful.
“Happy are you, O Israel. Who is like you, a people saved by the Lord (not through the powers of men, as other people), a shield of your help, and the sword of your triumph! Your enemies shall come fawning to you; and you shall tread upon their high places” (v. 29); as though he were saying: “With your powers you are not equal to your enemies, but He is powerful who is your sword.”
Now compare the song of Moses with these blessings, and you will see the contrast. There he condemns the whole people; here he blesses individuals, but on account of a promise made to the fathers. So on account of a few good ones the blessing is given to the whole people. Nevertheless, on account of evil men, both the people and their king, are finally destroyed after the good ones have been separated from their midst.
Luther’s works, vol. 9: Lectures on Deuteronomy 1525