Titus 1:9

9 He must hold firmly to the trustworthy message as it has been taught, so that he can encourage others by sound doctrine and refute those who oppose it.

Read Titus 1:9 Using Other Translations

Holding fast the faithful word as he hath been taught, that he may be able by sound doctrine both to exhort and to convince the gainsayers.
He must hold firm to the trustworthy word as taught, so that he may be able to give instruction in sound doctrine and also to rebuke those who contradict it.
He must have a strong belief in the trustworthy message he was taught; then he will be able to encourage others with wholesome teaching and show those who oppose it where they are wrong.