Let none henceforth seek needless cause to approve The faith they owe; when earnestly they seek Such proof, conclude they then begin to fail. Milton.Paradise Lost, Book IX. Line 1140.
Ever note, Lucilius, When love begins to sicken and decay, It useth an enforced ceremony; There are no tricks in plain and simple faith. Shakespeare.Julius Cæsar, Act IV. Scene 2. (Brutus to Lucilius.)