E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The reason why a stag symbolises Christ is from the superstition that it draws serpents by its breath from their holes, and then tramples them to death. (See Pliny: Nat. Hist., viii. 50.)
Stag in Christian art. The attribute of St. Julian Hospitaller, St. Felix of Valois, and St. Aidan. When it has a crucifix between its horns it alludes to the legendary tale of St. Hubert. When luminous it belongs to St. Eustachius.