[Esaias]

That is part of what Titus was to teach concerning slaves, that they were to be obedient and well-pleasing in all things, not "answering again" ie no back talking. They were not to be embezzling or stealing or appropriating for themselves from their masters but were to demonstrate they were totally faithful and trustworthy in all things. This would "adorn the teaching of God in all things", that is, it would adorn or beautify or glorify the doctrine of God (the Christian Way, the Gospel) in every area of their life.

Its about being personally above reproach in order to eliminate any possible reproach being brought on the Gospel.