'Sound' in the Bible

holding fast the faithful word which is in accordance with the teaching, so that he will be able both to exhort in sound doctrine and to refute those who contradict.

This testimony is true. For this reason reprove them severely so that they may be sound in the faith,

But as for you, speak the things which are fitting for sound doctrine.

Older men are to be temperate, dignified, sensible, sound in faith, in love, in perseverance.

sound in speech which is beyond reproach, so that the opponent will be put to shame, having nothing bad to say about us.