'Sound' in the Bible

Keep and follow the pattern of sound teaching (doctrine) which you have heard from me, in the faith and love which are in Christ Jesus.

For the time will come when people will not tolerate sound doctrine and accurate instruction [that challenges them with God’s truth]; but wanting to have their ears tickled [with something pleasing], they will accumulate for themselves [many] teachers [one after another, chosen] to satisfy their own desires and to support the errors they hold,