“Deceit is this world's passport: who would dare,
However pure the breast, to lay it bare?”

Source: Snow Falling on Cedars

The Dignity of Human Nature (1754)

Source: A Lover's Discourse: Fragments

Difesa miglior, ch'usbergo e scudo,
È la santa innocenza al petto ignudo.
Canto VIII, stanza 41 (tr. Alex. Cuningham Robertson)
Variant translation: Better defence than shield or breastplate, is holy innocence to the naked breast!
Gerusalemme Liberata (1581)

Beaumont and Fletcher Philaster, Act III, sc. ii, line 144.
These lines are used almost unaltered ("holds" becoming "does hold") in Act III, sc. ii of Buckingham's The Restauration, an adaptation of Philaster. They appear with an attribution to Buckingham in many 19th century collections of quotations, e.g. Henry George Bohn A Dictionary of Quotations from the English Poets (1867) p. 63, and hence also on several quotation websites.
Misattributed

Source: The Princess Bride