"The number of your days I will fulfill" (Exodus 23:26). It is written, "And he said to them: I am a hundred and twenty years old this day" (Deuteronomy 31:2). What does the verse teach by saying "this day"? This very day my days and my years were completed. This teaches you that the Holy One, blessed be He, fulfills the years of the righteous from day to day and from month to month, as it is said, "The number of your days I will fulfill." "I can no longer go out and come in" (Deuteronomy 31:2). What is meant by "go out and come in"? If you say it means going out and coming in literally, is it not written, "And Moses went up from the plains of Moab to Mount Nebo" (Deuteronomy 34:1), and it was taught that there were twelve steps there and Moses strode them in a single stride? Rather, "go out and come in" refers to matters of Torah, teaching that the gates of wisdom were closed to him.
God Completes the Years of the Righteous to the Very Day
Yalkut Shimoni on Torah 360:1
(שמות כג כו) אֶת מִסְפַּר יָמֶיךָ אֲמַלֵּא. כְּתִיב (דברים לא, ב) "וַיֹּאמֶר אֲלֵהֶם בֶּן מֵאָה וְעֶשְׂרִים שָׁנָה אָנֹכִי הַיּוֹם". מַה תַּלְמוּד לוֹמַר "הַיּוֹם". הַיּוֹם מָלְאוּ יָמַי וּשְׁנוֹתָי. לְלַמֶּדְךָ, שֶׁהַקָּדוֹשׁ בָּרוּךְ הוּא מַשְׁלִים שְׁנוֹתֵיהֶן שֶׁל צַדִּיקִים מִיּוֹם לְיוֹם וּמֵחֹדֶשׁ לְחֹדֶשׁ, שֶׁנֶּאֱמַר אֶת מִסְפַּר יָמֶיךָ אֲמַלֵּא. "לֹא אוּכַל עוֹד לָצֵאת וְלָבוֹא". מַאי לָצֵאת וְלָבֹא, אִילֵימָא לָצֵאת וְלָבֹא מַמָּשׁ, וְהָכְתִיב (שם לד, א) "וַיַּעַל מֹשֶׁה מֵעַרְבֹת מוֹאָב אֶל הַר נְבוֹ", וְתַנְיָא, שְׁתֵּים עֶשְׂרֵה מַעֲלוֹת הָיוּ שָׁם וּפְסָעָן מֹשֶׁה בִּפְסִיעָה אַחַת, אֶלָּא לָצֵאת וְלָבֹא בְּדִבְרֵי תוֹרָה, מְלַמֵּד שֶׁנִּסְתְּמוּ מִמֶּנּוּ שַׁעֲרֵי חָכְמָה.