Ask your ass if he believes it

• ask your ass → Lazare Sainéan, La Langue de Rabelais (Paris 1922): 16th century storytellers would begin their tales with the formula, Au temps que les bêtes parlaient, “In the days when animals could speak”

• if he believes it → Lazare Sainéan, La Langue de Rabelais (Paris 1922), quotes the closing line from François Rabelais, Pantagruel, Chapter 1: Car si ne le croiez, non foys je, fist elle, “For if you do not believe it- 'Indeed I don't!' said she”