Hello all. This is my first post here. It looks like a very interesting forum!
In regards to your verses, I think its useful to look at the whole section that they come from.
A Tree and Its Fruit
15"Watch out for false prophets. They come to you in sheep's clothing, but inwardly they are ferocious wolves. 16By their fruit you will recognize them. Do people pick grapes from thornbushes, or figs from thistles? 17Likewise every good tree bears good fruit, but a bad tree bears bad fruit. 18A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit. 19Every tree that does not bear good fruit is cut down and thrown into the fire. 20Thus, by their fruit you will recognize them.
21"Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of heaven, but only he who does the will of my Father who is in heaven. 22Many will say to me on that day, 'Lord, Lord, did we not prophesy in your name, and in your name drive out demons and perform many miracles?' 23Then I will tell them plainly, 'I never knew you. Away from me, you evildoers!'
(NIV)
Now fruit here does not directly relate to deeds, else he would be saying that salvation depends on deeds which would directly contradict numerous other verses (see Romans). Fruit here is pretty clearly the fruit of the spirit, which we see from Gal 5 is:
22But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, 23gentleness and self-control. Against such things there is no law. 24Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. 25Since we live by the Spirit, let us keep in step with the Spirit. 26Let us not become conceited, provoking and envying each other.
Now, we are not perfect in living by this spirit but as born again Christians we have received the spirit of Christ (thats what being born again means) and we then have this spirit as our essential character. Yes, we struggle. We fall short. We produce imperfect fruit sometimes. We have productive years and unproductive years, but this fruit is the nature of a true Christian. When you see people who call themselves Christians who are by nature angry, judgemental, intolerant, etc. theres a pretty good chance that that is the fruit of a different kind of tree. We must remember, however, that it is Gods job to judge, not ours.
Also note that the fruit of the good tree will make you want to do good deeds, and not do bad deeds. So good deeds do flow from a true Christian (or perhaps I should say the will to do good deeds because in our imperfection we all too often do marginal or even bad things when we were trying to do good), but the deed itself is not required or a sign of salvation. Al Capone could walk a little old lady across the street. That doesnt make him a good guy, but it would be very difficult, in fact impossible, for Al Capone to portray the fruits of the spirit in such a way that you believed that they were his nature, (unless he turned to God and received the spirit, of course. Even Al could have been saved.)
Must run but this is an interesting forum. Good questions Snowy.