I only quote others the better to quote myself.

[Je ne dis les autres, sinon pour d’autant plus me dire.]

Michel de Montaigne (1533-1592) French essayist

Essays, Book 1, ch. 25 (1.25), “Of the Education of Children [De l’institution des enfans]” (1579) [tr. Screech (1987), 1.26]
    (Source)

This essay was in the 1st (1588) edition, but this passage was added as of the 3rd (1595) ed. Some translators use the 1588 sequence of chapters, not the 1595, and so identify this as ch. 26.

(Source (French)). Alternate translations:

I never spake of others, but that I may the more speake of my selfe.
[tr. Florio (1603)]

Neither have I said so much of others, but to get a better opportunity to explain myself.
[tr. Cotton (1686); Cotton/Hazlitt (1877)]

I quote others only in order the better to express myself.
[tr. Hazlitt/Wight (1879)]

I do not quote others, save the more fully to express myself.
[tr. Ives (1925), 1.26]

I do not speak the minds of others except to speak my own mind better.
[tr. Frame (1943), 1.26]

I only quote others to make myself more explicit.
[tr. Cohen (1958), 1.26]