Annulo Dei figuram ne gestato
(In). Wear not God's image in a ring (or inscribe....), the 24th symbol of the
Protretics. Jamblicus tells us that Pythagoras wished to teach by this prohibition that God had an “incorporeal subsistence.” In fact, that it meant “thou shalt not liken God to any of His works.”
Probably the ring, symbolising eternity, bore upon the special prohibition.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894