4 is a number of completion, creation, and the world. It is often used in relation to God's creation. There are 4 regions of eart: North, East, South, West, as there are 4 divisions of the day: morning, afternoon, evening, and night, as well as 4 season of the year: summer, autumn, winter, spring.

After the creation of man (Adam), God made the garden of Eden, and in that garden was a river that was separated into 4 headwaters: Pishon, which ran through the land where there was gold; Gihon, Tigris, and Euphrates.

Revelations talks about the 4 horse men of the Apocalypse, and 4 angels standing ready at the 4 corners of the earth. There are 4 Gospels in the bible, and lots more references can be seen.