Did your parents or teachers ever drill something into you when you were a kid so that you couldn't forget it? I'm guessing that most of us would answer yes.
I think it's that way with the Scriptures, too. When something is repeated often and insistently in Scripture, you get the feeling that we had better pay close attention and take it very seriously!
So, I can't help thinking that way about the Scriptural emphasis on sound doctrine. I identified about a dozen passages that speak to us about the importance of sound doctrine or correct teaching, and would like to share them here.
PASTORAL LETTERS
St. Paul's First Letter to Timothy lists several categories of sin and sexual immorality as being "contrary to sound doctrine" (1 Tim. 1:10). He also encourages Timothy to instruct the brethren as a "good minister of Christ Jesus, nourished on the words of faith and of the good doctrine which you have followed" (1 Tim. 4:6).
In the Second Letter to Timothy, Paul exhorts Timothy to "follow the pattern of sound words which you have heard from me..." (2 Tim. 1:13). He also tells Timothy to "guard the truth that has been entrusted to you by the Holy Spirit who dwells within us" (2 Tim. 1:14). In chapter 4, Paul warns Timothy that "the time is coming when people will not endure sound teaching...and will turn away from listening to the truth and wander into myths" (2 Tim. 4:3-4).
When St. Paul writes to Titus, he describes the qualities that Church elders and bishops should demonstrate. A bishop, Paul says, "must hold firmly to the sure word as taught, so that he may be able to give instruction in sound doctrine and also to convince those who contradict it" (Titus 1:9). He charges Titus, "But as for you, teach what befits sound doctrine" (Titus 2:1). Paul continues, "in your teaching show integrity, gravity, and sound speech that cannot be censured..." (Titus 2:7-8).
LETTERS OF JOHN
The Letters of John also insist on sound doctrine. John's Second Letter warns that "Anyone who goes ahead and does not abide in the doctrine of Christ does not have God" (2 John 9). John also says that if anyone comes to you without teaching doctrine that is sound, true and correct - don't let him into your house or even give him a greeting (cf. 2 John 10). That is how seriously the word of God considers this matter!
The same thought continues as well in the Third Letter of John. The author says that nothing could bring him greater joy than to hear that his children "follow the truth" (3 John 4). In another place he says that his partners in spreading the gospel are "fellow workers (or cooperators) in the truth" (3 John 8). An interesting point is that Benedict XVI chose this phrase for his motto when he was named a bishop.
GOOD GUYS AND BAD GUYS
When I was a kid growing up, I watched a lot of cowboy movies. There was always a "good guy," the hero, that we all rooted for, as well as a "bad guy," the villain, that we all booed. The good guy wore a white hat and always won! Human nature is always quick to find its "good guys and bad guys," even when that identification is superficial and simplistic.
For example, it's trendy these days to paint something like "sound doctrine" as a "bad guy," that is somehow opposed to being pastoral or compassionate - just like "law" is considered a "bad guy" and "mercy" is always a "good guy." The problem with this way of thinking is that it doesn't reflect reality, nor for that matter, the word of God. Based on the Scripture texts above, and others besides, we neglect sound doctrine to our own peril.