Theologians frequently talk of “Pauline theology” and “Peterine theology” as though the apostles formulated their own doctrinal platforms.
Paul’s claim was that his message was divine. Hear him. God “in his own seasons manifested his word in the message, wherewith I was entrusted according to the commandment of God our Savior” (1:3). The apostle’s message was God’s word! Could a declaration of inspiration be plainer?
Compare with this Paul’s discussion of the origin of the gospel which he proclaimed as found in Galatians 1.
“For I make known to you, brethren, as touching the gospel which was preached by me, that it is not after man. For neither did I receive it from man, nor was I taught it, but it came to me through revelation of Jesus Christ” (vv. 11, 12).
So bracket Titus 1:3, and in your margin record: Paul’s inspiration. See Galatians 1:11, 12.