To be a saint is the exception. To be a good man is the rule. Err, weaken and sin, but be among the good.
 
[Être un saint, c’est l’exception ; être un juste, c’est la règle. Errez, défaillez, péchez, mais soyez des justes.]

Victor Hugo (1802-1885) French writer

Les Misérables, Part 1 “Fantine,” Book 1 “An Upright Man,” ch. 4 (1.1.4) (1862) [tr. Donougher (2013)]
    (Source)

Part of the short summary of Bishop Myriel's teachings. (Source (French)). Alternate translations:

To be a saint is the exception; to be upright is the rule. Err, falter, sin, but be upright.
[tr. Wilbour (1862); Wilbour / Fahnestock / MacAfee (1987)]

To be a saint is the exception, to be a just man is the rule. Err, fail, sin, but be just.
[tr. Wraxall (1862)]

To be a saint is the exception; to be an upright man is the rule. Err, fall, sin if you will, but be upright.
[tr. Hapgood (1887)]

To be a saint is to be an exception; to be a true man is the rule. Err, fail, sin if you must, but be upright.
[tr. Denny (1976)]