John Calvin Commentary Luke 24:50

"And he led them out until [they were] over against Bethany: and he lifted up his hands, and blessed them." — Luke 24:50 (ASV)

And lifted up his hands, and blessed them; by which He showed that the office of blessing, which was enjoined on the priests under the Law, truly and properly belonged to Himself. When people bless one another, it is nothing more than praying on behalf of their fellow believers; but with God it is different, for He does not merely benefit us by wishes, but by a simple act of His will grants what is desirable for us.

But while He is the only Author of all blessing, yet, so that people might obtain a clear understanding of His grace, He chose that initially the priests should bless in His name as mediators. Thus Melchizedek blessed Abraham (Genesis 14:19), and in Numbers 6:23-27, a perpetual law was established regarding this matter. To this same effect, we read in Psalm 118:26, We bless you out of the house of the Lord.

In short, the apostle tells us that to bless others is a mark of superiority, for the less, he says, is blessed by the greater (Hebrews 7:7). Now when Christ, the true Melchizedek and eternal Priest, was revealed, it was necessary that what had been foreshadowed by the figures of the Law should be fulfilled in Him. As Paul also shows, we are blessed in Him by God the Father, so that we may be rich in all heavenly blessings (Ephesians 1:3). Openly and solemnly He once blessed the apostles, so that believers may go directly to Him if they desire to share in His grace.

In the lifting up of the hands, an ancient ceremony is described which, we know, was formerly used by the priests.