We should take care also that the punishment shall not be out of proportion to the offence, and that some shall not be chastised for the same fault for which others are not even called to account.

[Cavendum est etiam, ne maior poena quam culpa sit, et ne isdem de causis alii plectantur, alii ne appellentur quidem.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher

De Officiis [On Duties; On Moral Duty; The Offices], Book 1, ch. 25 (1.25) / sec. 89 (44 BC) [tr. Miller (1913)]
    (Source)

(Source (Latin)). Alternate translations:

Diligent care should be taken, in the next place, that the penalty be proportioned to the nature of the crime; and that some do not pass without ever being questioned, while others are punished for the same misdemeanours.
[tr. Cockman (1699)]

Great care too must be taken, that the punishment be not greater than the offence; and that some should not be punished for the same offences, for which others are not called to account.
[tr. McCartney (1798)]

We ought, likewise, to take care that the punishment be proportioned to the offence, and that some be not punished for doing things for which others are not so much as called to account.
[tr. Edmonds (1865)]

Care also must be taken lest the punishment be greater than the fault, and lest for the same cause some be made penally responsible, and others not even called to account.
[tr. Peabody (1883)]

Again, we should never impose a penalty disproportioned to the offence or for the same crime punish one and let another go unchallenged.
[tr. Gardiner (1899)]

We must take care that the punishment is not in excess of the crime, and that it is not inflicted on some only while others equally guilty are not even brought to trial.
[ed. Harbottle (1906)]

One should also be careful that the punishment does not surpass the crime and that some people receive beatings while others do not even receive a reprimand.
[tr. Edinger (1974)]