1. Be discerning. Test them.
1 John 4:1
Dear friends, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world.
Matthew 7.15-16
15 ‘Watch out for false prophets. They come to you in sheep’s clothing, but inwardly they are ferocious wolves. 16 By their fruit you will recognise them.
Revelation 2:22
I know your deeds, your hard work and your perseverance. I know that you cannot tolerate wicked people, that you have tested those who claim to be apostles but are not, and have found them false. 3 You have persevered and have endured hardships for my name, and have not grown weary.
2. Do not associate with false teachers
Romans 16:17-18
17 I urge you, brothers and sisters, to watch out for those who cause divisions and put obstacles in your way that are contrary to the teaching you have learned. Keep away from them. 18 For such people are not serving our Lord Christ, but their own appetites. By smooth talk and flattery they deceive the minds of naïve people.
2 John 1:10-11
10 If anyone comes to you and does not bring this teaching, do not take them into your house or welcome them. 11 Anyone who welcomes them shares in their wicked work.
3. Oppose them
Ephesians 5:11
Have nothing to do with the fruitless deeds of darkness, but rather expose them.
1 Timothy 1:3-4
3 As I urged you when I went into Macedonia, stay there in Ephesus so that you may command certain people not to teach false doctrines any longer 4 or to devote themselves to myths and endless genealogies. Such things promote controversial speculations rather than advancing God’s work – which is by faith.
Titus 1:10-16
10 For there are many rebellious people, full of meaningless talk and deception, especially those of the circumcision group. 11 They must be silenced, because they are disrupting whole households by teaching things they ought not to teach – and that for the sake of dishonest gain. 12 One of Crete’s own prophets has said it: ‘Cretans are always liars, evil brutes, lazy gluttons.’ 13 This saying is true. Therefore rebuke them sharply, so that they will be sound in the faith 14 and will pay no attention to Jewish myths or to the merely human commands of those who reject the truth. 15 To the pure, all things are pure, but to those who are corrupted and do not believe, nothing is pure. In fact, both their minds and consciences are corrupted. 16 They claim to know God, but by their actions they deny him. They are detestable, disobedient and unfit for doing anything good.
4. Persevere in faithfully preaching and teaching the word of God
2 Timothy 4:1-22
In the presence of God and of Christ Jesus, who will judge the living and the dead, and in view of his appearing and his kingdom, I give you this charge: 2 preach the word; be prepared in season and out of season; correct, rebuke and encourage – with great patience and careful instruction. 3 For the time will come when people will not put up with sound doctrine. Instead, to suit their own desires, they will gather round them a great number of teachers to say what their itching ears want to hear. 4 They will turn their ears away from the truth and turn aside to myths. 5 But you, keep your head in all situations, endure hardship, do the work of an evangelist, discharge all the duties of your ministry.
1 Timothy 4 is also highly relevant. The instructions to Timothy include:
Point out their errors (v.6)
Avoid godless talk (v.7)
Instead train yourself to be godly (v.7)
Labour and strive (v.10)
Command and teach (v.11)
Set an example in speech, conduct, love, faith and purity (v.12)
Devote yourself to the public reading of scripture, to teaching and preaching (v.13)
Use your spiritual gift (v.14)
Be diligent and committed (v.15)
Watch your life and doctrine closely (v.16)
Persevere in them and you will save both yourself and others (v.16)