Courage is not simply one of the virtues, but the form of every virtue at the testing point, which means, at the point of highest reality. A chastity or honesty, or mercy, which yields to danger will be chaste or honest or merciful only on conditions. Pilate was merciful till it became risky.

C. S. Lewis (1898–1963) English writer, literary scholar, lay theologian [Clive Staples Lewis]

The Screw-Tape Letters, #29 (1942)
    (Source)

See Johnson (1775), Stevenson (1880), Barrie (1922).