The Bible often uses a plant, such as a tree, illustratively. Sometimes this draws on the fact that as a seed sprouts and grows, the roots develop before the boughs, other branches, or fruit being supported by the roots. For example, Isaiah 37:31 reads: “Those who escape of the house of Judah, those who are left remaining, will certainly take root downward and produce fruitage upward.”​—Job 14:8, 9; Isaiah 14:29.

The language at Isaiah 37:31 and Malachi 4:1 draws on the fact that boughs (and the fruit on secondary branches) derive their life from the root. This is a key to understanding how Jesus is the “root of Jesse” and the “root of David.”