"And this for Yehuda" (Deut. 33,7)

A kabbalistic approach: When Moses said the words, “v’zot l’Yehuda,” he addressed the emanation malchut, the emanation from which the hereditary dynasty of Yehuda draws its divine input. It is this emanation that gives the kings of Yehuda the power to wage war successfully.

Interestingly, David, a king descended from Yehuda, refers to the same emanation as when he proclaimed: "if war overtakes me, I put my faith in zot," (Psalms 27:3) the emanation from which my forefather Yehuda drew his strength. The emanation malchut sometimes referred to as zot is featured repeatedly in the life of David. (Psalms 99:4 and 72:1) This is the reason that David was successful in all his many wars.

This is also why he never fails to give thanks to the Lord Who was the source of his success. The whole formula ‘Lamnatzeah mizmor l‘david’ is evidence that David attributed his success to, “The One Who grants victory.” Because the kings of Yehuda enjoyed the assistance of the attribute/emanation malchut, it was doubly important for David to acknowledge that ultimately success is rooted in the Primal Cause, in G‑d.

[Selected with permission from the seven-volume English edition of "The Torah Commentary of Rebbeinu Bachya" by Eliyahu Munk.]