Or HaChaim on Deuteronomy 31:2/אור החיים על דברים ל״א:ב׳

1 לא אוכל עוד לצאת ולבא, "I am no longer able to go out and come in" (lead you in war). Moses attributed his inability to do so to the fact that he had already lost control over his soul the one which bore his name, as we explained in the name of the Zohar. It had already departed from him.

2He also wanted to explain to the people why he was convinced that he would die on that day. While we have already supplied the reason for this, it is not in the nature of the righteous to let on to their peers that they have some superior perceptions; this would be arrogant. This is why Moses cited two different reasons. 1) I am unable to lead you in war, i.e. I no longer have G'd's permission to do so. This permission has now been given Joshua. 2) G'd has told me: "you will not cross this river Jordan." From these two indicators it was clear to him that he had outlived his usefulness and was about to die.

3The letter ו before the word השם is to be understood as the reason for the word היום Moses had used immediately before.

4The sequence of the words וה׳ אמר אלי, "and the Lord had said to me, etc." which follow so closely on Moses' statement: I cannot go out, etc." indicate his loyalty as a servant of the Creator. He suggested by this sequence that if, per chance, this same G'd would now give him instructions to cross the Jordan, he, Moses, would gird himself and be ready to lead the Israelites across though he did not feel capable of doing so at this moment. The only reason he did not insist on doing so was that G'd had told him not to.