As a matter of self-preservation, a man needs good friends or ardent enemies, for the former instruct him and the latter take him to task.
The Things which hurt, instruct. - Benjamin Franklin
The Bible will teach you, correct you, instruct you, and give you hope. - Elizabeth George
Laws are partly formed for the sake of good men, in order to instruct them how they may live on friendly terms with one another, and partly for the sake of those who refuse to be instructed, whose spirit cannot be subdued, or softened, or hindered from plunging into evil. - Plato
When you wish to instruct, be brief; that men's [children's] minds take in quickly what you say, learn its lesson, and retain it faithfully. Every word that is unnecessary only pours over the side of a brimming mind. - Marcus Tullius Cicero
It is always safe to learn, even from our enemies; seldom safe to venture to instruct, even our friends. - Charles Caleb Colton
Statements make sense for somebody who needs advice. I’m not giving advice. I don’t instruct. At my best, I delight. That’s my job. - Ron Koertge
Much as a teacher may wince at the thought, he is also an entertainer—for unless he can hold his audience, he cannot really instruct or edify them. - Sydney J. Harris
It is in vain for man to endeavor to instruct man in those things which the Holy Spirit alone can teach. - Pere La Combe
The surest way to corrupt a youth is to instruct him to hold in higher esteem those who think alike than those who think differently. - Friedrich Nietzsche
[Paul] has no intention to instruct the Christian community about the task and responsibility of government. His entire concern is with the responsibility of the Christian community towards the State. - Dietrich Bonhoeffer
When you wish to instruct, be brief; that men's minds take in quickly what you say, learn its lesson, and retain it faithfully. Every word that is unnecessary only pours over the side of a brimming mind. - Cicero
A book has but one voice, but it does not instruct everyone alike. - Thomas à Kempis