The First Set of 12 Stones
In Exodus 28, Moses received instructions regarding the priestly garments that Aaron and his son, the Levite, were to wear during their duties.

This created the original breastplate of the High Priest, which Aaron used to communicate with God.

Revelation 16:15 states that the breastplate was adorned with twelve precious stones in memory of the twelve tribes of Israel on the front.

The stones were engraved with the names of the twelve tribes of Israel, so that Aaron remembered them whenever he prayed.