We were happy, and wished to make all happy around us. False pleasures make men haughty and severe, and such pleasures are always selfish. But true happiness inspires gentleness and benevolence, and diffuses its influence on very hand.

[Nous étions heureux, & nous voulions vivre avec des gens qui le fussent. Le bonheur faux rend les hommes durs & superbes, & ce bonheur ne se communique point. Le vrai bonheur les rend doux et sensibles, & ce bonheur se partage toujours.]

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

“Arsaces and Ismenia [Arsace et Isménie]” (1742) [tr. 1797]
    (Source)

Commonly quoted in isolation, with just the second two sentences; often misattributed to his Pensées.

(Source (French)). Other translations:

We were happy ourselves; and were desirous of living with people that were so. False happiness renders men austere and haughty; and this happiness is selfish and unsociable. True felicity, on the contrary, softens them into sensibility and gentleness: it delights in reciprocal communication.
[tr. 1784]

We were happy, and we wished to live with people who were happy too. False happiness renders men rigid and haughty; and this happiness has nothing social. True happiness makes them mild, and endues them with sensibility; and this happiness is always shared.
[tr. 1785]

[...] False happiness renders men stern and proud, and that happiness is never communicated. True happiness renders them kind and sensible, and that happiness is always shared.
[tr. 1854]