“Ambition prompted many to become deceitful; to keep one thing concealed in the breast, and another ready on the tongue; to estimate friendships and enmities, not by their worth, but according to interest; and to carry rather a specious countenance than an honest heart.”
Ambitio multos mortales falsos fieri subegit, aliud clausum in pectore, aliud in lingua promptum habere, amicitias inimicitiasque non ex re, sed ex commodo aestimare, magisque vultum quam ingenium bonum habere.
Variant translation: It is the nature of ambition to make men liars and cheats, to hide the truth in their breasts, and show, like jugglers, another thing in their mouths, to cut all friendships and enmities to the measure of their own interest, and to make a good countenance without the help of good will.
Source: Bellum Catilinae (c. 44 BC), Chapter X, section 5