Inspired by another thread, I thought to share some thoughts on this issue.
When the fruit are indicators by which we know people, it is the wolves in sheep's clothing it is speaking about. I think the actual fruit they are betrayed with is fruit of the knowledge of good and evil. The whole passage there is speaking in Garden terms. There is a WAY that leads to LIFE and a way that leads to Destruction, much like the two trees. The forbidden tree would render death while Life would give... well... Life. Genesis even mentions the WAY OF THE TREE OF LIFE after Adam was expelled.
We read of a corrupt tree and a good tree in the narrative. And good trees cannot bear corrupt fruit and corrupt trees cannot bear good fruit.
Wolves in Sheep's clothing do not even really know they ARE wolves, in one sense. While the MANY never find the narrow way to Life, we read MANY call Jesus "Lord, Lord," perform miracles in His name, and are not known by the Lord. The Lord KNOWS HIS SHEEP. Not the wolves.
To ensure wolves do not pull it over on us, Jesus said a good tree cannot bring forth corrupt fruit.
But we reads the wolves appeal, as though they are stupefied as to their inability to enter the Kingdom/Way of Life, to miracles, deliverances and prophecies they gave in Jesus' name. Jesus responds saying He never knew them and tells them they work iniquity. He said we must hear His words and do them in order to enter the Kingdom and be like a house on a rock that cannot fall.
So, wolves see miracles, call Jesus Lord, but they HAND OUT THE FORBIDDEN FRUIT. Knowledge of good and evil. It sounds SO SPIRITUAL. Knowing what is good and what is evil. Experts on what not to do and what to do. But IT IS NOT LIFE.
They do not take their crosses and follow Christ. Sheep follow the Lord and know His voice to the extent that they hear it AND DO IT. They take their crosses. Those crosses remove the works of iniquity that wolves possess causing the Lord to not "know" them.
The fruit wolves hand out is certainly not Life. I believe it is "touch not, taste not, handle not." Self-righteousness where the cross is replaced with self-exaltation.
LIFE empowers us by the Spirit and inspires us to do things while we not requiring codebooks or Law to learn to do or not to do. The way
Gal 5 talks about the Spirit is that we find ourselves living lives that the Law condones, without ever having resorted to law by a code-book mentality to learn what and what not to do.
Jesus did not come that we might have knowledge of good and evil. He came to give LIFE. But when you think of it, most of Christianity (the "many") offer knowledge of good and evil. "This" is right, "that" is wrong. When people offer fruit repeating over and over that we must not do THIS or do THAT, we are being handed fruit of the knowledge of good and evil. And wolves are dishing it out to us.