And Aaron shall offer the Levites before the LORD for an offering of the children of Israel, that they may execute the service of the LORD.

Wesley's Notes

8:11 For an offering - Heb. for a wave - offering. Not that Aaron did so wave them, which he could not do, but that he caused them to imitate that motion, and to wave themselves toward the several parts of the world: whereby they might signify their readiness to serve God, according to their capacity wheresoever they should be.

King James Translators' Notes

offer: Heb. wave

offering: Heb. wave offering

they...: Heb. they may be to execute, etc

Jamieson-Fausset-Brown Bible Commentary

11-13. And Aaron shall offer the Levites-Hebrew, "as a wave offering"; and it has been thought probable that the high priest, in bringing the Levites one by one to the altar, directed them to make some simple movements of their persons, analogous to what was done at the presentation of the wave offerings before the Lord. Thus were they first devoted as an offering to God, and by Him surrendered to the priests to be employed in His service. The consecration ceremonial was repeated in the case of every Levite who was taken (as was done at a later period) to assist the priests in the tabernacle and temple. (See on [66]2Ch 29:34).

Matthew Henry's Concise Commentary

8:5-26 Here we have directions for the solemn ordination of the Levites. All Israel must know that they took not this honour to themselves, but were called of God to it; nor was it enough that they were distinguished from others. All who are employed for God, must be dedicated to him, according to the employment. Christians must be baptized, ministers must be ordained; we must first give ourselves unto the Lord, and then our services. The Levites must be cleansed. They must be clean that bear the vessels of the Lord. Moses must sprinkle the water of purifying upon them. This signifies the application of the blood of Christ to our souls by faith, that we may be fit to serve the living God. God declares his acceptance of them. All who expect to share in the privileges of the tabernacle, must resolve to do the service of the tabernacle. As, on the one hand, none of God's creatures are his necessary servants, he needs not the service of any of them; so none are merely honorary servants, to do nothing. All whom God owns, he employs; angels themselves have their services.