וַיַּקְרֵב֙ אֶת־הָאַ֣יִל הַשֵּׁנִ֔י אֵ֖יל הַמִּלֻּאִ֑ים וַֽיִּסְמְכ֞וּ אַהֲרֹ֧ן וּבָנָ֛יו אֶת־יְדֵיהֶ֖ם עַל־רֹ֥אשׁ הָאָֽיִל׃
И был представлен другой баран, баран освящения, и Аарон и его сыновья возложили руки на голову барана.
Rashi
איל המלאים — This means the same as איל השלמים, for the word מלואים is synonymous with the word שלמים; this term is used to describe the ram because by means of it they set the priest fully (ממלאין) and completely (משלימין) in their priestly office (cf. Sifra, Tzav, Mechilta d'Miluim 1 20).
Ibn Ezra
He brought the other ram, the ram of installation, and Aaron and his sons placed [plural] their hands the earlier verse [Exodus 29:19] has, “Aaron and his sons shall place [singular] their hands….”. No difference in meaning here exists between the singular and plural forms of the verb. A great grammarian erred when he said that the meaning of the singular was that he alone was to place his hands first, followed by his sons; and that the plural meant that they all placed their hands together.
Ramban
AND HE PRESENTED THE OTHER RAM, THE RAM OF ‘HAMILU’IM’ (CONSECRATION). I have already explained208Exodus 28:41. that the meaning of “consecration” is that the priests should be fully empowered to perform the Divine Service, and that this term is applied to both the altar itself and to those who perform the Service. Thus all these offerings [the bullock of the sin-offering, the ram of the burnt-offering, etc.,] were brought for the purpose of consecrating the priests, as it is written, And this is the thing that thou shalt do unto them to hallow them, to minister unto Me in the priest’s office: take one young bullock and two rams without blemish.209Ibid., 29:1. The second ram, however, is here called specifically the ram of consecration, because it was the last of these offerings, and it was after it that their consecration was completed and they ministered before Him, blessed be He, for all these offerings were indispensable in the matter.
It is possible that the [purpose of the] sin-offering was to effect atonement for the altar and to sanctify it, for it is so written;210See Ramban above, Verse 15. and that the burnt-offering was to expiate for the priests, like the atonement effected by all freewill burnt-offerings,211See Ramban above, 1:4. and the second ram which was the peace-offering, was a thanksgiving to G-d for having given them in His house and within His walls a monument and a memorial.212See Isaiah 56:5. Thus it was only the peace-offering which was brought for the purpose of consecration, and therefore it alone is here called “the ram of milu’im” (consecration). It is called milu’im [in the plural, although the offering for that purpose was, according to this interpretation, only one], because the fats and the thigh as well as the heave-offering of the bread were all burnt.213Verses 25-28.
It is possible that the [purpose of the] sin-offering was to effect atonement for the altar and to sanctify it, for it is so written;210See Ramban above, Verse 15. and that the burnt-offering was to expiate for the priests, like the atonement effected by all freewill burnt-offerings,211See Ramban above, 1:4. and the second ram which was the peace-offering, was a thanksgiving to G-d for having given them in His house and within His walls a monument and a memorial.212See Isaiah 56:5. Thus it was only the peace-offering which was brought for the purpose of consecration, and therefore it alone is here called “the ram of milu’im” (consecration). It is called milu’im [in the plural, although the offering for that purpose was, according to this interpretation, only one], because the fats and the thigh as well as the heave-offering of the bread were all burnt.213Verses 25-28.