Is Jesus talking about supererogatory merit in Matt 5:38-48? i.e. earning a reward rather than sin I know the word "merit" will send up red flags for Protestants, but what I mean has nothing to do with justification.  By supererogatory merit I mean doing something not required, and doing it for the purpose of earning a reward (not of being justified).  The reason I ask the question is because normally I've read Matt 5:38-48 as a set of disjointed verses (reading it in the KJV which is always printed verse-by-verse).  But recently having read it in a few modern translations that arrange the verses in paragraphs, I noticed something interesting.

The verses on turning to the other cheek, giving your coat to anyone who sues for your shirt, loving your enemies, all seem to be connected to verse 46 "For if you love those who love you, what reward do you have?"  So its all about trying to earn a reward.  "And if you greet only your brothers, what more are you doing than others?"  Ah, and its about doing more than others!

This calls in question the traditional interpretation that its a sin to defend yourself, to defend yourself in a lawsuit, to hate your enemy, and presents these things as extras, something above and beyond for those who want to do more than others and earn a special reward.   

So my question is basically, what do you think?  Is there any basis to this interpretation or do you think its entirely wrong?
I don't think that Matt 5:38-48 is a depiction of the type of system you are describing. Rather, it appears to be Jesus doing something he often did, namely, turning the thoughts and traditions of man upside-down. When He says "you have heard it said...", he is referring to some Rabbi's teaching somewhere (that is how they often taught back then, similar to PhD's today quoting one another).

However, there IS a biblical basis to defend the type of system you are curious about. Read 1 Corinthians 3:10-15.

(NIV)
10 By the grace God has given me, I laid a foundation as a wise builder, and someone else is building on it. But each one should build with care. 11 For no one can lay any foundation other than the one already laid, which is Jesus Christ. 12 If anyone builds on this foundation using gold, silver, costly stones, wood, hay or straw, 13 their work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each person’s work. 14 If what has been built survives, the builder will receive a reward. 15 If it is burned up, the builder will suffer loss but yet will be saved—even though only as one escaping through the flames.

Paul says here that no one can lay another foundation (the foundation must be Christ), so, the foundation is your salvation or justification by Christ's body and blood (I, as a Protestant, would say "faith alone"). However, Paul also states that each man builds on this foundation using materials (your works and/or fruits, or merits), and that we will receive rewards according to how our works hold up in God's test (most likely on judgment day).

I hope that helped to answer your question.