"It is enough."

³⁶ He said to them, “But now if you have a purse, take it, and also a bag; and if you don’t have a sword, sell your cloak and buy one. ³⁷ It is written: ‘And he was numbered with the transgressors’; and I tell you that this must be fulfilled in me. Yes, what is written about me is reaching its fulfillment.”
³⁸ The disciples said, “See, Lord, here are two swords.”
   “That’s enough!” he replied."
                                                   -- Luke 22:36-38, NIV

Here is the same passage in the NASB version:

³⁶And He said to them, "But now, whoever has a money belt is to take it along, likewise also a bag, and whoever has no sword is to sell his coat and buy one.
³⁷"For I tell you that this which is written must be fulfilled in Me, 'and he was numbered with transgressors'; for that which refers to Me has its fulfillment."
³⁸They said, "Lord, look, here are two swords." And He said to them, "It is enough."
                                                 --Luke 22:36-38, NASB

My question is about verse 38.  What did Jesus mean when he said, "It is enough."?  Did he mean "Stop it!" or "That will be sufficient for our purposes."?  Why did he say that sentence?

The Greed word translated "enough" in this verse is hikanos, which means "sufficient, considerable, much, appropriate, competent, worthy, or deserving." (from The Strongest NIV Exhaustive Concordance.)  I have not been able to find any discussion of this Greek word hikanos that implies that it was ever used to mean "Stop it," as we in English would figuratively use the phrase "That's enough," to mean "Please quit what you are doing."  I must assume, therefore, that Jesus meant to say "That will be sufficient."

However, given what happens later, when the sword is used to cut off the high priest's servant's ear, Jesus did not mean that the swords should be used to defend Jesus against being arrested.  What, then, did he intend the disciples to do with the weapons?

Many commentaries, including my own NIV Study Bible, indicate that Jesus' statement was intended to be ironic or sarcastic.  "Sensing that the disciples had taken him too literally, Jesus ironically closes the discussion with a curt 'That's plenty!'" (Zondervan NIV Study Bible, 2002, p. 1615).  This, as well as several other commentaries, suggest that Jesus was using a figure of speech, and that he intended to convey the impression that the disciples would be facing much more opposition than they had in the past and would therefore not be able to rely on the generosity of strangers for their well-being, as they had in the past (Matthew 10:9; Mark 6:8; and Luke 9:3.)

One commentary that I read indicated that the word hikanos could have a time frame attached to it, as if Jesus was saying "That is enough talk about this for now."  If that is the case, then it makes a lot of sense that Jesus later rebuked his disciple for using the sword on the high priest's servant.  He did not intend for the followers to use weapons to defend themselves; he was merely using figurative language, much like he did in previous parables, to inform the disciples that they would need to be prepared their future ministry.

This interpretation might be supported by Ephesians 6:10-18, which talks about the "armor of God."  It is well understood that this passage was meant to be figurative, and that the saints are not meant to engage in violence of any kind. (See also Romans 13:1-7; Colossians 1:16; Titus 3:1-2; Hebrews 12:14; and 1 Peter 2:13-14, among others.)