It had a great and lofty wall and had twelve gates, and at the gates twelve angels, and names were inscribed which are those of the twelve tribes of the sons of Israel.

Revelation 21:11b-

After Adam’s expulsion, cherubs were posted in front of the original Paradise to keep out unclean humans. (Genesis 3:24) Similarly, angels are posted at each entrance of the holy city Jerusalem to ensure the spiritual security of the city. Indeed, throughout the last days, angels have been guarding the congregation of anointed Christians, which becomes New Jerusalem, from Babylonish contamination.​—Matthew 13:41.