15These things speak and exhort and reprove with all authority. Let no one disregard you.
Tit_2:15 "speak and exhort and reprove" There are three present active imperatives: continue teaching (cf. Tit_2:1), continue exhorting, and continuing reproving (cf. 2Ti_3:16). Church leaders must encourage the saints and recognize false teachers!
▣ "with all authority" Jesus is said to have all authority (exousia) in heaven and on earth (cf. Mat_28:18). He delegated this authority to His Apostles (Paul being the last, one born out of due time). Paul delegated his authority (epitaç) to both Timothy and Titus as his personal representatives.
Since the death of these eye-witnesses, the written New Testament (as well as the OT) has become the authority "for all subsequent generations of believers" (cf. 2Ti_3:15-17).