The Keys and the Sword

Peter with the keys of the kingdom and Paul with the sword of his beheading, the two princes of the apostles.

Peter holds keys because of the promise of the keys of the kingdom; Paul holds a sword because he was beheaded, and because of the sword of the spirit. The two are usually painted as a contrasting pair — Peter older, broad-faced and white-bearded, Paul balding with a long dark beard — so that a viewer could tell them apart at the far end of a nave, before any object was visible at all.