He that is already corrupt is naturally suspicious, and he that becomes suspicious will quickly become corrupt.
— Samuel Johnson

Plagiarists are always suspicious of being stolen from.
Samuel Taylor Coleridge suspicious quote

The least one can say of power is that a vocation for it is suspicious.
— Jean Rostand

Self-respect: the secure feeling that no one, as yet, is suspicious.
— H. L. Mencken

My father used to say: Never suspect people, It's better to be deceived or mistaken, which is only human, after all, than to be suspicious, which is common.
— suspicious quotation by Stark Young