(3) וילך משה וידבר את הדברים האלה אל כל ישראל. בן מאה ועשרים שנה אנכי היום, וגו', “Moses went and spoke these words to all of Israel. ‘I am 120 years old this day.’” It is possible that the 120 years Moses lived corresponded to the 120 days he spent on Mount Sinai. During the first 40 days he received the first set of Tablets. During the second 40 days he pleaded for G’d to forgive the people the sin of the golden calf; he spent the next 40 days on the mountain in order to receive the second set of Tablets. This may be the reason why he used the term אנכי instead of אני.
Our sages in Sotah 13 feel that he meant to say that on that day he was precisely 120 years old, i.e. that he died on the same day of the same month as he had been born. This may also be the reason why he used the word היום at the beginning of the previous Parshah, so that all these speeches took place on the same day. The day in question was the seventh day of Adar at the end of the Israelites 40th year in the desert. We have further proof of this in 34,8 where the Torah reported that the people mourned Moses for 30 days during which they did not journey. The Torah states explicitly that the days of Moses’ mourning came to an end. It is proper to read this verse in conjunction with Joshua 1,10: “Joshua commanded the law-enforcement officers of the people: ‘prepare for yourselves provisions for in another three days you will cross the river Jordan.’” Anyone reading these two verses together will realize that Joshua would not command the people to prepare these provisions until the mourning period for Moses had passed. To make this plain, the Torah had to write the verse: “the days of crying for (the death of) Moses had concluded.” The Book of Joshua 4,19 reports that the Jewish people completed crossing the river Jordan on the tenth of the first month, i.e. 3 days after the conclusion of the mourning period for Moses. By counting backwards you will arrive at the date of the 7th Adar as the date on which Moses had died. When the Torah in Exodus 2,3 reported that Moses’ mother was unable to hide him any longer, the date referred to is the 6th of Sivan, the day on which the revelation at Mount Sinai took place 80 years later. On that day, the light which filled only his parents’ home on the day he was born became so powerful that it shone for the whole Jewish nation. The light which had filled the house of Amram had already forecast the eventual greatness of the boy that had been born to Yocheved. The reason Yocheved had to hide Moses in a basket, well insulated, was that the light surrounding the baby had become so much stronger that it represented a danger to the family. The Torah speaks of Yocheved having hidden Moses for שלשה ירחים ‘three lunar months,” rather than שלשה חדשים, “three months,” (Exodus 2,2) to indicate that these were lunar months. The months Adar, Nisan, and Iyar are 29,30, and 29 days long, respectively. This gives us a total of 88 days during which Moses was kept “hidden” at home, or it takes us back to the 7th day of Adar as Moses’ birthday. From all this it becomes clear that Moses died on the same day of the same month on which he had been born. The word חדש implies a period which equals 1/12th of the year, something not subject to variation either by adding or subtracting from it. The same is not true of the period known as ירח, a period which may comprise either 29 or 30 days. The reason why the Torah used the term ירחים in the verse mentioned was to enable us to calculate the precise date on which Moses was born. This prompted our sages in Kiddushin 38 to state that G’d completes the life cycle of the righteous from day to day (to grant them whole years) something they base on Exodus 23,26: את מספר ימיך אמלא, “I will fill (round out) the number of your days (meaning “years”).