וַיַּעַל֩ אַהֲרֹ֨ן הַכֹּהֵ֜ן אֶל־הֹ֥ר הָהָ֛ר עַל־פִּ֥י יְהוָ֖ה וַיָּ֣מָת שָׁ֑ם בִּשְׁנַ֣ת הָֽאַרְבָּעִ֗ים לְצֵ֤את בְּנֵֽי־יִשְׂרָאֵל֙ מֵאֶ֣רֶץ מִצְרַ֔יִם בַּחֹ֥דֶשׁ הַחֲמִישִׁ֖י בְּאֶחָ֥ד לַחֹֽדֶשׁ׃
Umakyat si Aaron na saserdote sa bundok ng Hor ayon sa utos ng Walang-Hanggan, at doon siya namatay, sa ikaapatnapung taon mula nang lumabas ang mga anak ni Israel sa lupain ng Egipto, sa ikalimang buwan, sa unang araw ng buwan.
Tze'enah Ure'enah
“Aaron died there in the fortieth year after the Israelites had left the land of Egypt, on the first day of the fifth month” [33:38]. Aaron died in the fortieth year in the fifth month, that is the month of Ab, on the first day of the month. Our sages say: why did the verse say here on which day he died? When he died should have been written in the portion of Hukat, since the proper death of Aaron was written there. Furthermore, we do not find regarding our ancestors, Abraham, Isaac, and Jacob that the Torah writes on which day they died. However, the Torah does write on which day that Aaron died, on the first day of the month of Ab. The Canaanites thought that the month of Ab was good to wage war against Israel, since they will have it as a month of troubles and exile in the future. In particular, the clouds were removed and Aaron died. The Canaanite thought to himself, I will wage war with Israel. Therefore, it is written in this verse, “he died in the fifth month” [33:38]. This means that Aaron died in the fifth month, which is the month of Ab.7Bahya, Numbers, 33:38.
Rashi
'על פי ה [AND AARON THE PRIEST WENT UP TO MOUNT HOR] BY THE WORD (lit., BY THE MOUTH) OF THE LORD— This phrase tells us that he died by the Divine Kiss (Bava Batra 17a; cf. Rashi on Numbers 20:26).
Rabbeinu Bahya
בחדש החמישי באחד לחודש, “in the fifth month on the first of the month.” This was the New Moon on which Aaron died. On the ninth of that month (many hundreds of years later) the Temple was burned and the Torah with it. On the 7th of the month of Adar following Moses died, as is reported in Joshua that the Children of Israel crossed the river Jordan on the tenth of the first month (Nissan). You may deduct the three days that the people prepared food for the crossing and 30 days during which the people mourned their leader and you will find that Moses must have died on the 7th of Adar (compare Joshua 4,19 and 1,11).