Why did Moshe mention his age?
Ramban and Seforno: To console them on his death, 1 since, due to his advanced age, he was anyway not able to lead them into Eretz Cana'an.
Ramban: Though in reality, he was not affected by old age, as the Torah testifies in 34:7.
What are the implications of the word "ha'Yom"?
Rashi: It implies that his days and years were complete, because he was destined to die on the same date as he was born.
Sotah, 13b: It teaches us that Hashem completes the years of Tzadikim, from day to day and from month to month 1 - as the Torah wrote in Mishpatim Sh'mos 23:26 "es Mispar Yamecha Amalei".
See Torah Temimah, note 1.
What is "Lo Uchal Od Latzeis Velavo" referring to?
Rashi #1 and Ramban #1 (citing the Ibn Ezra): It is referring to crossing the Yarden (or leading the troops - Ramban, Ibid.), as the Pasuk goes on to explain. 1
Rashi #2 and Ramban #2 (citing Sotah, 1t is referring to the fact that he could no longer teach Torah [because the traditions and fountains of Chochmah were closed to him (by Divine Decree). 2
Why was Moshe no longer able to come and go?
Rashi: Because Hashem had withdrawn the authority from him and handed it to Yehoshua - as the Pasuk goes on to explain. 1
Ramban #2 and Seforno: Both due to old age and because Hashem had withdrawn the authority from him - as the Pasuk goes on to explain.
Rashi: It cannot mean on account of old age
