Matthew 5:21-24 appears in the Sermon on the Mount and reads:

[21] You have heard that it was written of old: Do not murder.  But whoever would murder shall be liable to judgment. [22] But I say to you that everyone who has anger against his brother shall be liable to judgment. And anyone who would say to his brother, “Stupid!” shall be liable to the Sanhedrin. And anyone who would say “moron!” shall be liable to Gehenna of fire. [23] There if you are offering a gift upon the altar and remember that your brother has something against you, [24] leave the gift there before the altar and depart first to reconcile with your brother, and then come and offer the gift. 

The Sermon on the Mount is a passage that has been especially central to my thinking around what the obligations are for Christian behavior, and particularly when I was younger I was inclined to read passages as a literal call for perfection in behavior. My thinking has subsequently changed, and I think there is a fairly subtle argument that is advanced here by Jesus.  Verse 21 is a straightforward reference to mosaic law. Verse 22 makes the novel argument that anger against your brother is equivalent to murder, and then further suggests that insulting your brother makes you liable to judgment in the Sanhedrin. If this is referring to the main Sanhedrin, this seems quite unlikely, but even in the case of local or regional Sanhedrins it is doubtful that name-calling would have risen to their attention (in my experience even the parents of children sometimes find it difficult to care about their childrens’ name-calling).  This is then escalated further by suggesting that name-calling will land you in “Gehenna of fire.” It should be noted that the words I’ve translated as “stupid” and “moron” are respectively the Aramaic and Greek words for the same thing.  

This term “Gehenna of fire” is also worth further consideration, because here we find a place where reading the Bible translation can be misleading.  The Greek here is γέενναν τοῦ πυρός geennan tou pyros and literally means “Gehenna of fire,” but in the King James Version, NIV, and NRSV, this phrase is translated as some variation of the “hell of fire” or “fire of hell.”  The reason this is misleading is that Gehenna is a valley that actually exists near Jerusalem, and although by the time Matthew was composed Gehenna had apparently taken on significance as a place of divine punishment, this is not necessarily the same thing as hell in the sense that we commonly understand it, and more likely refers to something equivalent to the physical resurrection of the dead on earth during the day of judgment, with the people found lacking then cast into the fire (to be burned up rather than punished eternally). Another possibility here is that the wicked go to the fire of Gehenna on judgment day and simply have their inequities burned away, as per Zechariah’s cleansing fire that purifies like silver in a smelter.  

Verses 23-24 add a new wrinkle to the passage.  Here we see Jesus say that prior to making offerings to God, we should reconcile with people.  It is important to remember that while the Temple existed, core religious practice centered around sacrificial offerings of incense, grain, animals, etc.  Those offerings were intended to atone for transgressions that individuals and the people collectively had committed, and people were required to be in a state of ritual purity to make the offerings (so as not to offend God).  Ritual purity for the average person required circumcision for men, observing dietary restrictions, as well as ritual washing after certain unclean acts like sex, menstruation, childbirth.  Certain spaces within the Temple were more sacrosanct than others, and so it was only specific members of the priestly caste in certain circumstances who were able to enter the holy of holies, for example.  This concept of ritual purity prior to sacrifice is quite foreign to contemporary Christian practice, but at the time Matthew was composed would have been obvious to his mostly Jewish audience. 

Rereading Matthew 5:22-24 with this idea of ritual purity in mind, it seems that Jesus first identifies a state of actual impurity per Mosaic law (committing murder), makes anger equivalent to it and liable to both wordly religious and divine judgment, and then in vv. 22-24 talks about reconciliation with your brother in a way that implies it as a precondition of ritual purity.  This implication is obviously a novel argument with little foundation in Hebrew Scripture.  

Generally I read this passage as a rebuke of the legalism of the scribes and Pharisees (it should be noted that Matthew 5:20 reads “unless your righteousness would greatly exceed the scribes and Pharisees, you will surely not enter the Kingdom of Heaven”), both by manufacturing a new standard not found in the law (which Jesus accuses them of in Matthew 15:1-9), and also because this new standard is just a very kind and human-centered standard (as opposed to essentially stealing money from your parents, which is the example in Matthew 15:1-9). This deserves its own series of posts someday, but generally I read many of the examples in Matthew 5 in this same light, with Jesus essentially demanding impossible perfection in several aspects.  This message, I think is softened in Matthew 6:12 (“Forgive us our debts, as we forgiven those indebted to us”), 6:14-15 (“For if you would forgive their transgression to people, your heavenly father will also forgive you transgressions; but if you would not forgive for people, neither will your heavenly father forgive your transgressions”), and Matthew 7:2 (“For by the judgment with which you judge, you shall be judged; and with the measure by which you measure, you shall be measured”).

For the most part Matthew 5:21-24 does not see parallels in the other Gospels, and is unique to Matthew.  The closest thing to a parallel passage is Mark 11:25, which reads:

And when you stand praying, forgive if you have something against someone, so that your father in heaven will also forgive your transgressions.

My Greek New Testament annotates this as a parallel passage in the sense of being thematically similar to Matthew 5:23, but obviously it is far from a direct quote.  It is, however, telling that the closest parallel to this passage in Matthew also echoes the language of reciprocity that we have considered above.  It is also telling that this passage is largely unique to Matthew, especially since many parts of the Sermon on the Mount have parallel passages in Luke.  This passage represents Matthew’s particular emphases, and sets the tone for the entire chapter by contrasting Christian righteousness against that of the scribes and Pharisees.  

There is also the question of how exactly we should take the reference to Gehenna of fire.  One possible reading here is that Jesus is actually mocking the scribes and Pharisees for elevating trivial offenses to the point of divine wrath, another is that punishment in Gehenna of fire is easily sidestepped by simply forgiving other people their transgressions.  It is unclear how seriously, then, we should take this reference to fire, and to the extent that it seems related to our two thirds shall perish one third shall be purified with fire, it is by implicitly placing the scribes and Pharisees among the two thirds who shall perish.  To the extent that I am willing to make that argument, it would be to say: I think that both Matthew’s reference to Zechariah elsewhere and his criticism of scribes and Pharisees here are two facets of a the same larger project, wherein he argues that Christianity is the proper heir to the Hebrew religion, rather than the Pharisees (who ultimately evolved in Rabbinical Judaism).