'Sin' in the Bible

Suffer not thy mouth to cause thy flesh to sin; neither say thou before the angel, that it was an error: wherefore should God be angry at thy voice, and destroy the work of thine hands?

For there is not a single righteous man on earth who practices good and does not sin.

I gave my mind to knowledge and to searching for wisdom and the reason of things, and to the discovery that sin is foolish, and that to be foolish is to be without one's senses.