Adam Clarke on Titus 2:8

Sound speech - Λογον ὑγιη· Sound or healing doctrine. Human nature is in a state of disease; and the doctrine of the Gospel is calculated to remove the disease, and restore all to perfect health and soundness. All false doctrines leave men under the influence of this spiritual disease; the unadulterated doctrine of the Gospel alone can heal men.

He that is of the contrary part - Whether this may refer to the Judaizing teachers in general, or to some one who might, by his false doctrine, have been disturbing the peace of the Churches in Crete, we cannot tell.

Having no evil thing to say of you - Against a person who is sound in his doctrine, and holy in his life, no evil can be justly alleged. He who reports evil of such a person must be confounded when brought to the test. Instead of περι ὑμων, of You, περι ἡμων, of Us, is the reading of CDEFG, and about forty others; with both the Syriac, all the Arabic, Slavonic, Vulgate, Itala, and several of the primitive fathers. This reading makes a better sense, and is undoubtedly genuine.