'Sound' in the Bible

clinging to the faithful word according to the doctrine taught, that he may be able both to encourage with sound teaching and refute gainsayers.

This testimony is true; for which cause rebuke them severely, that they may be sound in the faith,

But do thou speak the things that become sound teaching;

that the elder men be sober, grave, discreet, sound in faith, in love, in patience;

a sound word, not to be condemned; that he who is opposed may be ashamed, having no evil thing to say about us: