The first half of the chapter has an odd chronology. The chapter opens with Moshe carving the new tablets and coming down from the mountain:

“At that time the LORD said to me: Carve two tablets of stone like the first, and come up to Me on the mountain… I carved two tablets of stone like the first, and I went up the mountain with the two tablets in my hand.” (Deuteronomy 10:1–3)

בָּעֵת הַהִוא אָמַר ה׳ אֵלַי פְּסָל־לְךָ שְׁנֵי לֻחֹת אֲבָנִים כָּרִאשֹׁנִים וַעֲלֵה אֵלַי הָהָרָה…

וָאֶפְסֹל שְׁנֵי־לֻחֹת אֲבָנִים כָּרִאשֹׁנִים וָאַעַל הָהָרָה וּשְׁנֵי הַלֻּחֹת בְּיָדִי

Moshe then states that God rewrote the tablets and that he placed them in the Ark:

“He wrote on the tablets, according to the first writing, the Ten Commandments… and I turned and came down from the mountain and placed the tablets in the Ark which I had made.” (Deuteronomy 10:4–5)

וַיִּכְתֹּב עַל־הַלֻּחֹת כַּמִּכְתָּב הָרִאשׁוֹן אֵת עֲשֶׂרֶת הַדְּבָרִים…

וָאֵפֶן וָאֵרֵד מִן־הָהָר וָאָשִׂים אֶת־הַלֻּחֹת בָּאָרוֹן אֲשֶׁר עָשִׂיתִי

Then, somewhat abruptly, Moshe inserts a travel notice and recounts Aaron’s death:

“From Beeroth-bene jaakan the Israelites marched to Moserah. Aaron died there and was buried there, and his son Eleazar became priest in his stead.” (Deuteronomy 10:6)

Immediately following Aaron’s death, Moshe mentions the elevation of the tribe of Levi:

“At that time the LORD set apart the tribe of Levi to carry the Ark of the Covenant of the LORD… therefore Levi has no portion or inheritance with his brothers; the LORD is his inheritance.” (Deuteronomy 10:8–9)

בָּעֵת הַהִוא הִבְדִּיל ה׳ אֶת־שֵׁבֶט הַלֵּוִי לָשֵׂאת אֶת־אֲרוֹן בְּרִית ה׳…

Only afterward does Moshe return to the subject of his time on the mountain:

“I stayed on the mountain, as on the first occasion, forty days and forty nights; and the LORD heeded me once again.” (Deuteronomy 10:10)

וְאָנֹכִי עָמַדְתִּי בָּהָר כַּיָּמִים הָרִאשֹׁנִים אַרְבָּעִים יוֹם וְאַרְבָּעִים לָיְלָה וַיִּשְׁמַע ה׳ אֵלַי גַּם בַּפַּעַם הַהִוא

This chronology is puzzling. The second tablets were crafted very soon after Moshe broke the first tablets. It was only after the giving of the Torah entirely that God commands the building of the Mishkan, and has Moshe appoint the tribe of Levi as caretakers. Aaron, however, does not die until year forty, 38 years after the events at Har Sinai. This leads us to two questions about chapter 10: Why is Aaron’s death recounted here? And when exactly was this “second” forty day period on the mountain?

Ibn Ezra explains that Moshe deliberately connects Aaron’s death to the sin of the Golden Calf. According to this view, Moshe was able to defer Aaron’s punishment for thirty eight years, but not eliminate it entirely. The Malbim adds that Moshe’s message is that while he successfully interceded on behalf of the people, he was unable to save Aaron. Aaron’s exclusion from the land, like Moshe’s own, ultimately traces back to the sin of the Golden Calf.

As for the forty days and nights, Rashi explains that this verse simply supplies information missing from verse 2—namely, the duration of Moshe’s stay on the mountain. While Rashi’s explanation addresses the textual gap, it does not explain why this single stay is interrupted by references to Aaron’s death and the appointment of the Levites.

Perhaps, taking Ibn Ezra and the Malbim together, one can conclude that this entire first section of the chapter forms a single thematic unit. Moshe’s ascent to receive the second tablets also included sustained prayer on behalf of both the people and his brother. The eventual death of Aaron thirty eight years later, the replacement of the firstborn by the tribe of Levi, and the preservation of the nation itself all flow from that same forty day and forty night period of intercession. Moshe’s prayer secured forgiveness for the people, the second tablets, the elevation of the Levites—and only a partial, delayed mitigation of the decree against Aaron.