This canto deals with the Hypocrites, represented by Caiaphas. For their punishment, they are forced to wear coats that are beautiful on the outside, but lined inside with heavy lead, forcing them to bend over and struggle to move. This punishment fits the sin since they glitter on the outside but are so weighted down that there is no chance of spiritual progress.
Dante uses the fable of the mouse and the frog (then attributed to Aesop) as an allegory to describe the scene in Cantos XXII between the demons and the escaped sinner. The fable goes that a mouse wanted to cross a pond and asked a frog to help him. The frog, wanting to drown the mouse, suggested that he take the mouse across on his back. The mouse agreed, but was afraid of falling off, so the frog suggested that the mouse tie himself to the frog. When they reach the middle of the pond, the frog decides to dive under and pull the mouse with him. However, a hawk, seeing the struggling mouse, catches it, taking the frog with him. In Dante's comparison, the sinner represents the mouse and the demons that fell into the pitch represent the frog. There are several disagreements about which creature represents what.