A.T. Robertson Commentary Titus 2:8

"sound speech, that cannot be condemned; that he that is of the contrary part may be ashamed, having no evil thing to say of us." — Titus 2:8 (ASV)

Sound (υγιη, Attic usually υγια in accusative singular), elsewhere in Pastorals participle υγιανων (verse 1).

That cannot be condemned (ακαταγνωστον). Only N.T. example (verbal, α privative and καταγνωστος) and in IV Macc. 4:47. Deissmann (Bible Studies, p. 200) quotes it from an inscription and the adverb from a papyrus.

He that is of the contrary part (ο εξ εναντιας). "The one on the opposite side" (your opponent). Cf. verse 9; 1 Timothy 5:14.

May be ashamed (ινα εντραπη). Final clause with ινα and second aorist passive subjunctive of εντρεπω, to turn, in middle and passive to turn one on himself and so be ashamed (to blush) as in 2 Thessalonians 3:14; 1 Corinthians 4:14. This sense in the papyri.

Evil (φαυλον). Old word, easy (easy morals), worthless; bad, as in 2 Corinthians 5:10.