^21:13There were three gates on the east and three gates on the north and three gates on the south and three gates on the west.

There were

three GATES on the east and
three GATES on the north and
three GATES on the south and
three GATES on the west.

Here we sense vaguely the way the tribes of Israel where encamped around the tabernacle (Numbers 2). The tribe of Judah was one of those on the east side. Jesus Christ is from the tribe of Judah (Revelation 5:5) and that is perhaps why the three GATES from the east are listed first. Otherwise, the east, north, south, and west listing may only indicate that if you are a resident of the new Jerusalem, you can enter it from any direction. In other words, all true believers (the wife of Christ in verse 9) are welcomed into the city.

Spiritually, with the angelic gatekeepers representing the 12 tribes of the sons Israel (previous verse), we all, Jew and non Jew, enter only in light of the eternal covenant God made with Abraham. The passport for each of us, formerly dead as Ephesians 2:1-10 puts it, is issued written in the blood of Jesus Christ. Jesus as the firstborn from the dead (Revelation 1:5) is the only one who can grant us that privilege. So even here in the 12 GATES we see another side of the Revelation of Jesus Christ.