HENRY: What stronger breastplate than a heart untainted?
Thrice is he armed that hath his quarrel just,
And he but naked, though locked up in steel,
Whose conscience with injustice is corrupted.

William Shakespeare (1564–1616) English dramatist and poet

Henry VI, Part 2, Act 3, sc. 2, l. 240ff (3.2.240-243) (1591)
    (Source)

See Ward.