The rainbow in the morning
Is the shepherd's warning;
The rainbow at night
Is the shepherd's delight. [ Proverb ]

A rainbow in the morning
Is the Shepherd's warning;
But a rainbow at night
Is the Shepherd's delight. [ Old Weather Rhyme ]

I know
The past and thence I will essay to glean
A warning for the future, so that man
May profit by his errors, and derive
Experience from his folly;
For, when the power of imparting joy
Is equal to the will, the human soul
Requires no other heaven. [ Shelley ]

No longer mourn for me when I am dead.
Than you shall hear the surly sullen bell
Give warning to the world that I am fled. [ William Shakespeare ]

One thorn of experience is worth a whole wilderness of warning. [ Lowell ]

He that gives time to resolve, gives time to deny, and warning to prevent. [ Proverb ]

To the warning word no man has respect, only to the flattering and promising is his attention directed. [ Johann Wolfgang von Goethe ]

Gunpowder is the emblem of politic revenge, for it biteth first and barketh afterwards; the bullet being at the mark before the noise is heard, so that it maketh a noise not by way of warning, but of triumph. [ Fuller ]

No good or lovely thing exists in this world without its correspondent darkness; and the universe presents itself continually to mankind under the stern aspect of warning, or of choice, the good and the evil set on the right hand and the left. [ John Ruskin ]

You can throw yourselves away. You can become of no use in the universe except for a warning. You can lose your souls. Oh, what a loss is that! The perversion and degradation of every high and immortal power for an eternity! And shall this be true of any one of you? Will you be lost when One has come from heaven, traveling in the greatness of His strength, and with garments dyed in blood, on purpose to guide you home - home to a Father's house - to an eternal home? [ Mark Hopkins ]