The Bible uses a large variety of metaphors, imagery, similes, types, parables, allegories, and analogies as teaching tools. They are used either to hide or cloud a meaning from outsiders, or sometimes to make them clear—so that God's people understand either way. Here, in Exodus 4:21, Israel is shown as a cohesive body—as a single, human son. In other places, Israel is portrayed as a virginal woman, married to God, and in yet other places, as a harlot who is still legally married but who, in reality, has left the marriage and pursued lovers.
In like manner, the church is typified as a body (of which Christ is the Head) and the firstborn of God. In another analogy, the church is portrayed as the firstfruits—not a body, but an assembly of individuals harvested as a crop. In another place, it is pictured as a loaf of bread that has leaven in it. The New Testament contains many other symbols for the church.
John W. Ritenbaugh
New Covenant Priesthood (Part 1)