The principle underlying every society is justice, for yourself and for others. If you are to love your neighbour as yourself, neighbour as yourself, it’s only fair to love yourself as much as you love your neighbour.

[Le principe de toute société est de se rendre justice à soi-même et aux autres. Si l’on doit aimer son prochain comme soi-même, il est au moins aussi juste de s’aimer comme son prochain.]

Nicolas Chamfort (1741-1794) French writer, epigrammist (b. Nicolas-Sébastien Roch)

Products of Perfected Civilization [Produits de la Civilisation Perfectionée], Part 1 “Maxims and Thoughts [Maximes et Pensées],” ch. 5, ¶ 321 (1795) [tr. Parmée (2003), ¶ 205]
    (Source)

See Matthew. (Source (French)). Alternate translations:

The one great social principle is to be just both to yourself and to others. If you must love your neighbour as yourself, it is at least as fair to love yourself as your neighbour.
[tr. Hutchinson (1902)]

Justice to oneself and to others is the first principle of all Society; and if we should love our neighbour as ourself, it is quite as just that we should love ourself as much as our neighbour.
[tr. Mathers (1926)]

The principle of all society is to do justice to oneself and to others. If one should love one’s neighbor as oneself, it is at least equally just to love oneself as one does one’s neighbor.
[tr. Merwin (1969)]

The principle of all society is to do justice to oneself and to others. If it is right to love the person next to us as ourselves, it is at least as right to love ourselves as much as the people next to us.
[tr. Siniscalchi (1994)]