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.