Points from these selected verses. 

16All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, 17that the man of God may be complete, equipped for every good work.

4I charge you in the presence of God and of Christ Jesus, who is to judge the living and the dead, and by his appearing and his kingdom: 2preach the word; be ready in season and out of season; reprove, rebuke, and exhort, with complete patience and teaching. 3For the time is coming when people will not endure sound teaching, but having itching ears they will accumulate for themselves teachers to suit their own passions....

...7I have fought the good fight, I have finished the race, I have kept the faith....