An honest man’s the noblest work of God.  Alexander Pope.

One’s mere word should be as trustworthy as a signed agreement attested by legal witnesses.
Curtis Vaughan

If faith does not make a man honest, it is not an honest faith
C. H. Spurgeon

Honesty is a question of right and wrong, not a matter of policy.
Anon.

Truth is always strong, no matter how weak it looks, and falsehood is always weak, no matter how strong it looks.
Phillips Brooks

Always tell the truth. Then you don’t have to worry about what you said last.
Robert Cook

Do not merely speak the truth, but live truthfully, openly and honesty with one another.
Sinclair Ferguson

Truth in propositions is powerful; truth in example is more powerful.
David Thomas

O faithful Christian, search the truth, hear truth, learn truth, love truth, speak the truth, hold the truth till death.
John Hus

Truth needs no flowers of speech.
Alexander Pope

Honest errors, openly admitted, are sooner forgiven. (Anon)

Madison Sarratt, longtime dean of men at Vanderbilt University and a teacher in the mathematics department, died in 1978. He wrote:

“Today I am going to give you two examinations, one in trigonometry and one in honesty. I hope you will pass them both, but if you must fail one, let it be trigonometry, for there are many good [people] in this world today who cannot pass an examination in trigonometry, but there are no good [people] in the world who cannot pass an examination in honesty.”  (More Perfect Illustrations)