Buvez le coup de l’étrier = Drink the stirrup-cup.
A franc étrier = At full speed. (See [Bride] and [Train].)
Évangile
C’est l’Évangile (or, c’est parole d’Évangile) = It is gospel truth.
Excuser
*Qui s’excuse, s’accuse = If you try to excuse yourself you practically acknowledge that you have done wrong; A guilty conscience needs no accuser.
Excusez du peu (ironic.) = Only that? How modest!
Exemple
Il prêcha d’exemple = He practised what he preached; He set the example.