Believers must teach and defend sound doctrine

Scripture references

1 Timothy 4:1–6 (ASV)

But the Spirit saith expressly, that in later times some shall fall away from the faith, giving heed to seducing spirits and doctrines of demons, 2through the hypocrisy of men that speak lies, branded in their own conscience as with a hot iron; 3forbidding to marry, and commanding to abstain from meats, which God created to be received with thanksgiving by them that believe and know the truth. 4For every creature of God is good, and nothing is to be rejected, if it be received with thanksgiving: 5for it is sanctified through the word of God and prayer.

6If thou put the brethren in mind of these things, thou shalt be a good minister of Christ Jesus, nourished in the words of the faith,...

Titus 1:9 (ASV)

9holding to the faithful word which is according to the teaching, that he may be able both to exhort in the sound doctrine, and to convict the gainsayers.

Titus 2:1 (ASV)

But speak thou the things which befit the sound doctrine:

Stories

Charles Finney walked into a tailor's shop where Dr. S was espousing the unbiblical doctrine of universal salvation. Taking the opportunity at hand, Mr. Finney argued brilliantly, with love, in defense of solid doctrine.