John Calvin Commentary Numbers 6:22

"And Jehovah spake unto Moses, saying," — Numbers 6:22 (ASV)

And the Lord spoke to Moses. A part of the priestly duties, which are constantly mentioned in the Law, is briefly set forth here. For God says that He had appointed the priests to bless the people. David seems to allude to this in the words:

We have blessed you out of the house of the Lord. (Psalms 118:26)

This doctrine is especially profitable, so that believers may confidently assure themselves that God is reconciled to them, when He ordains the priests to be witnesses and heralds of His paternal favor towards them. The word to bless is often used for praying for blessings, which is the common duty of all pious people. However, this rite (as we will see a little further on) was an efficacious testimony of God’s grace, as if the priests carried the commandment to bless from His own mouth.

But Luke shows that this was truly fulfilled in Christ when he relates that He lifted up His hands, according to the solemn rite of the Law, to bless His disciples (Luke 24:50). In these words, then, the priests were appointed ambassadors to reconcile God to the people, and this in the person of Christ, who is the only sufficient surety of God’s grace and blessing. Therefore, inasmuch as they then were types of Christ, they were commanded to bless the people. But it is worthy of remark that they are commanded to pronounce the form of benediction audibly, and not to offer prayers in an obscure whisper. From this, we gather that they preached God’s grace, which the people might apprehend by faith.