'Sound' in the Bible

holding to the faithful word which is according to the teaching, that he may be able to exhort in the sound doctrine, and to convict those who contradict him.

This testimony is true. For this cause, reprove them sharply, that they may be sound in the faith,

But say the things which fit sound doctrine,

that older men should be temperate, sensible, sober minded, sound in faith, in love, and in patience: