כֹּה־אָמַר֮ אֲדֹנָ֣י יְהוִה֒ בָּֽרִאשׁוֹן֙ בְּאֶחָ֣ד לַחֹ֔דֶשׁ תִּקַּ֥ח פַּר־בֶּן־בָּקָ֖ר תָּמִ֑ים וְחִטֵּאתָ֖ אֶת־הַמִּקְדָּֽשׁ׃
Так говорит Господь Бог: в первый месяц, в первый день месяца, возьми молодого тельца без порока; и ты очистишь святилище.
Tze'enah Ure'enah
“Thus says the Lord” [45:18]. Thus says God, on the first of Nisan the priest should take an ox that has no blemish and you should purify the Temple with it.
Rashi
So says the Lord God: In the first month, on the first of the month, you shall take a young bull [and] without blemish This is the bull of investiture mentioned at the beginning of this section (43:18 27), and he teaches [us] here that the investiture should be on the first of Nissan.