We have said that the laws were the particular and precise institutions of a legislator, and manners and customs the institutions of a nation in general. Hence it follows that when these manners and customs are to be changed, it ought not to be done by laws; this would have too much the air of tyranny: it would be better to change them by introducing other manners and other customs.

[Nous avons dit que les loix étoient des institutions particulieres & précises du législateur, & les mœurs & les manieres des institutions de la nation en général. De-là il suit que, lorsque l’on veut changer les mœurs & les manieres, il ne faut pas les changer par les loix ; cela paroîtroit trop tyrannique: il vaut mieux les changer par d’autres mœurs & d’autres manieres.]

Charles-Lewis de Secondat, Baron de Montesquieu (1689-1755) French political philosopher

Spirit of Laws [The Spirit of the Laws; De l’esprit des lois], Book 19, ch. 14 (1748) [tr. Nugent (1750)]
    (Source)

(Source (French)). Other translations:

We have said that the laws were the particular and precise institutions of the legislator and the mores and manners, the instructions of the nation in general. From this it follows that when one wants to change the mores and manners, one must not change them by the law, as this would appear to be too tyrannical; it would be better to change them by other mores and other manners.
[tr. Cohler/Miller/Stone (1989)]

We have said that laws were particular and precise institutions of the legislator, and the morals and the manners institutions of the nation as a whole. Whence it follows that when you want to change morals and manners, you should not do it by laws, which would appear too tyrannical; it is better to change them with other morals and manners.
[tr. Stewart (2018)]