Titus 1:9 English Standard Version (ESV)
9 He must hold firm to the trustworthy word as taught, so that he may be able to give instruction in sound[a] doctrine and also to rebuke those who contradict it.
2 Timothy 1:13 English Standard Version (ESV)
13 Follow the pattern of the sound[a] words that you have heard from me, in the faith and love that are in Christ Jesus.
Titus 2:1 English Standard Version (ESV)
Teach Sound Doctrine
2 But as for you, teach what accords with sound[a] doctrine.
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