To where did Moshe go?
(31,1) “And Moshe went and spoke these words to all Yisrael. And he said to them: I am one hundred and twenty years old today; I am no longer able to go out and come in.”
The commentaries ask on the phrase “And Moshe went” - to where did he go? But it seems to me that we can explain this phrase in accordance with the teaching of Chazal that a Tzaddik is described as one who is going or walking, as it says in Zechariah 3:7 “Thus said the Lord of Hosts: If you walk in My ways and you keep My charge, you too shall judge My house, and you too shall guard My courtyards, and I will make you as one who walks amongst these who are standing”. And the reason why a Tzaddik is called this is because he is constantly accumulating mitzvos and good deeds, and thus is constantly going forward.
Now, the gemora in Sotah 13b asks what Moshe meant when he said “I am no longer able to go out and come in”, and answers that he meant that he was no longer able to go out and come in - to give and take - in words of Torah, and this teaches us that the wellsprings of wisdom were closed to him. But since the wellsprings of wisdom were closed to him, maybe the wellsprings of the mitzvos were also closed to him, and the phrase “I am no longer able to go out and come in” means that Moshe no longer had the power to be considered as being active in doing good deeds.
To exclude this possibility the posuk starts with the words “And Moshe went”, to teach us that he still was considered 'going' with respect to good deeds. And the proof for this is that Moshe “spoke these words to all Yisrael”, because his admonition to Yisrael to learn wisdom and keep the mitzvos is itself a mitzvah. From this it is clear that he was 'going out and coming in' with respect to good deeds as before, and therefore when he said “I am no longer able to go out and come in” he was referring only to Torah and not to good deeds.
Incidentally, this explanation of “I am no longer able to go out and come in” - that the wellsprings of wisdom were closed to him, fits well with what it says later, “Assemble to me all the elders of your tribes and your officers” (31,28). Rashi explains there that although they normally blew two silver trumpets to assemble the people, on that day the trumpets were not used, to fulfil that which is taught in Koheles 8:8 that “one does not rule on the day of (one’s) death”.
But it seems to me that an additional reason why they did not blow the trumpets is because blowing trumpets is a symbol of kingship, because it is the way of a king to decree that his servants, the people, should come to him. But it is only appropriate for a person to decree that someone should come to him when a great person is commanding a lesser person. But if they are equal it is not appropriate that one should decree on the other to come to him, and all the more so a lesser person to a greater person. Instead, he should request that the person should come.
Therefore, as long as Moshe Rabbeinu was wise in Torah he was greater than all of Yisrael in all aspects of greatness, and so he could decree upon them to come to him. Therefore, he used the trumpets to obligate them to come. But now that the wellsprings of wisdom were closed to him, although he was still greater than them in deeds, they were greater than him in Torah. Therefore, he did not want to decree upon them to come and instead he honored them by requesting that they come to him, and thus he said “assemble to me” - as a request and not as a decree.
How was Moshe able to make all Yisrael totally righteous?
(31,30) “And Moshe spoke in the ears of all the assembly of Yisrael the words of this song until their completion.”
The phrase “until their completion” is difficult to understand, because obviously Moshe didn’t leave out any words.
But it seems to me that we can explain it according to the teaching of Chazal that words which come from the heart, penetrate the heart. Therefore, when Moshe Rabbeinu reproved Yisrael with the words of this song, he reproved them so well that they repented completely and became tzaddikim.
This is what the posuk is saying: “Moshe spoke in the ears of all the assembly of Yisrael the words of this song until their (Yisrael’s) completion” - until they became unblemished and totally righteous in their deeds.