What does it mean, you will recognize them by their fruits?

Sinclair Ferguson preached on the Sermon on the Mount in a recent series (Sermon on the Mount)
In the second-to-last sermon called Ultimate Choices delivered on January 3, he taught about how we recognize the false ones by their fruit. There are some spiritual tests to discern whether they are true or not. He said (and I recommend the entire half-hour sermon!)

You will recognize them by their fruits. What does this mean? 

1. Does this person remind me of the character and speech of the Lord Jesus Christ? Spiritual fruit in scripture, especially in the NT, is first and foremost likeness to Jesus in character and in speech. Alas, so often, that spiritual test will enable you to see thru a spiritual charlatan. 

2. And then you need to ask the question what is the fruit if this ministry and those who are influenced by it? What is the fruit of this teaching as you see the impact of it? Jesus is saying not only look at the person’s teaching and their character, but look at the impact he makes on others. 

See if this person’s teaching enables them to grow in fruit of the spirit. See if what he teaches sets them free from himself, to live for the glory of God. 

3.Many will say Lord Lord, didn’t we prophesy in your name etc … Jesus will say to them depart from me I never knew you. Here, Jesus is teaching us to distinguish, to judge, to discern between the possession of abilities that impress us, and the presence of grace that draws us to Jesus Christ. It’s possible to preach wonderfully eloquently, to prophesy, but apparently not really be a genuine Christian believer. 

4. The test is this- does the teaching draw my eyes to the Lord Jesus? Or does it draw my eyes to him, her, the gifts they have, the impression they make? It is this that helps us make the judgment of whether we follow this teacher.

In the January 2 sermon from the same series, called Condemnation and Discernment, Ferguson looked at the verse from Matthew 7, "Judge not, that you be not judged" is the most misunderstood teaching from the Sermon on the Mount. Jesus who says judgment in the form of condemning is dangerous, but judgment in the form of discerning is absolutely essential."

I recommend that half-hour sermon also.