פירוש על ויקרא 9:4

כי היום ה' נראה אליכם FOR TODAY THE LORD WILL APPEAR UNTO YOU to make His Shechinah rest upon your handiwork; on this account these sacrifices come (are to be brought) as an obligation for this day (cf. Sifra, Shemini, Mechilta d'Miluim 2 4).

כי היום ה' נראה, and the fire will emerge from heaven to consume the sacrifices on the altar.

כי היום ה' נראה אליכם, it had already become manifest as an appreciation of their handiwork when we read that the Presence (glory) of the Lord filled the Tabernacle (Exodus 40,34). It is therefore no more than appropriate that you express your appreciation of this by this sacrifice.