And one of the elders saith unto me, Weep not: behold, the Lion of the tribe of Juda, the Root of David, hath prevailed to open the book, and to loose the seven seals thereof. The Lion of the tribe of Juda - Jesus Christ, who sprang from this tribe, as his genealogy proves; see on Matthew 1:2 (note), Matthew 1:3 (note) and Luke 3:23 (note). There is an allusion here to Genesis 49:9, Judah is a lion's whelp; the lion was the emblem of this tribe, and was supposed to have been embroidered on its ensigns.
The Root of David - See Isaiah 11:1. Christ was the root of David as to his Divine nature; he was a branch out of the stem of Jesse as to his human nature.
Hath prevailed - By the merit of his incarnation, passion, and death.
To open the book - To explain and execute all the purposes and decrees of God, in relation to the government of the world and the Church.