The saying is trustworthy, and I want you to insist on these things, so that those who have believed in God may be careful to devote themselves to good works."
(Titus 3:8 ESV)
William Mounce has this to say:
The discussion flows smoothly from one thought into the next. ταυτων, "these things," refers back at least to the creed in vv 5-7, but there is little in those verses that warrants the use of the strong διαβεβαιουσθαι, "to insist emphatically." It is the Cretan's poor behavior that is causing the problem.
Mounce, The Pastoral Epistles, pg. 452
Does he mean this nothing in verses 5-7?
He saved us, not because of works done by us in righteousness, but according to his own mercy, by the washing of regeneration and renewal of the Holy Spirit, whom he poured out on us richly through Jesus Christ our Savior, so that being justified by his grace we might become heirs according to the hope of eternal life.”
(Titus 3:5-7 ESV)
Isn't that the whole purpose of the Pauline gospel pockets laced throughout the pastoral epistles? To form the basis of obedience. Insist on the gospel, and good works will follow!