Four is associated with the created world and its completeness — the four corners of the earth, the four winds, the four rivers of Eden, the four seasons. It speaks of the whole earth under God's rule.
When Scripture uses four, it often signals universality: the gospel going to all four corners, and God's reign extending over the whole created order.
The Number Four in Scripture
And after these things I saw four angels standing on the four corners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, nor on the sea, nor on any tree.