Judas represents the wolf in sheep's clothing, a type of person commonly found in Christian communities. In speaking to the church at Ephesus, Paul says, "I know that after I leave, savage wolves will come in among you and will not spare the flock. Even from your own number men will arise and distort the truth in order to draw away disciples after them." Acts 20:29,30 And in 1Cor 5:12,13 "What business is it of mine to judge those outside the church? Are you not to judge those inside? God will judge those outside. Expel the wicked man from among you."
Although Jesus knew Judas to be one of these, yet he allowed him to stay in order to fulfill the prophecy of his betrayal. But what was the purpose of the prophecy? I think it was to be a paradigm for future generations of Christian communities. Until he produced his fruit, Judas was not recognized as a wicked man. And thus Christians should not judge one another to be such a person until sufficient evidence arises. This, I think, is also the point of the parable of the wheat and the tares.
Judas reveals his true character is John 12:5,6 where Mary had generously poured out expensive perfume on Jesus' feet. Judas responded: "Why wasn't this perfume sold and the money given to the poor? It was worth a year's wages." He did not say this because he cared about the poor but because he was a thief; as keeper of the money bag, he used to help himself to what was put into it. Such wolves tend to be religious hypocrites. Because they don't value the spiritual, they'll insult the believers by rebuking them for wasting their lives on spiritual things while they could be meeting practical social needs, while themselves not doing so. They like to hold the money bag, asking for contributions for the poor, while wasting large amounts on "administrative costs" and neglect the more essential spiritual needs. While giving an appearance of being religious, in reality they are thiefs. However, be careful not to judge when there is no basis to do so. For it was not clear what Judas was doing until after the fact. There are many sincere believers concerned from social concerns, as Paul writes in his encounter with the apostles in Jerusalem: "All they asked was that we should continue to remember the poor, the very thing I was eager to do." Gal 2:10
There are those who will betray you with a kiss. They feign friendship. They are not one in spirit. Yet they may be someone you are discipling. They may be a fellow Christian involved in ministry. Unless you have the discernment of Christ you will not recognize who they are until they betray you. "Dear friends, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world." 1John 4:1 The most common way such people will betray you these days is by slandering you to "officials", who themselves may have some agenda against you. This is the kind of thing you will experience when you are involved in ministry as Jesus was. It is a part of the Christian life. So when these occur don't get discouraged, but rejoice that you can identify with Christ. "I want to know Christ and the power of his resurrection and the fellowship of sharing in his sufferings, becoming like him in his death" Php 3:10
My enemies say of me in malice, "When will he die and his name perish?" Whenever one comes to see me, he speaks falsely, while his heart gathers slander; then he goes out and spreads it abroad. All my enemies whisper together against me; they imagine the worst for me, saying, "A vile disease has beset him; he will never get up from the place where he lies." Even my close friend, whom I trusted, he who shared my bread, has lifted up his heel against me. Ps 41:5-9"You know how I am scorned, disgraced and shamed; all my enemies are before you. Scorn has broken my heart and has left me helpless; I looked for sympathy, but there was none, for comforters, but I found none. They put gall in my food and gave me vinegar for my thirst." Ps 69:19-21"Many are those who are my vigorous enemies; those who hate me without reason are numerous, Those who repay my good with evil slander me when I pursue what is good." Ps 38:19,20"O unbelieving and perverse generation," Jesus replied, "how long shall I stay with you? How long shall I put up with you?" Mt 17:17"Consider him who endured such opposition from sinful men, so that you will not grow weary and lose heart." Heb 12:3
Verses quoted from the NIV version