From: Matthew 13:47-53
(Jesus said to His disciples,)  "Again, the Kingdom of Heaven is like a net which was thrown into the sea and gathered fish of every kind;  when it was full, men drew it ashore and sat down and sorted the good into vessels but threw away the bad.  So it will be at the close of the age. The angels will come out and separate the evil from the righteous,  and throw them into the furnace of fire; there men will weep and gnash their teeth.
 "Have you understood all this?" They said to Him, "Yes."  And He said to them, "Therefore every scribe who has been trained for the Kingdom of Heaven is like a householder who brings out of his treasure what is new and what is old."
 And when Jesus had finished these parables He went away from there.
47. "Fish of every kind": almost all the Greek manuscripts and early translations say "All kinds of things". A dragnet is very long and about two meters wide; when it is extended between two boats it forms double or triple mesh with the result that when it is pulled in it collects all sorts of things in addition to fish--algae, weeds, rubbish, etc.
This parable is rather like the parable of the cockle, but in a fishing context: the net is the Church, the sea the world.
We can easily find in this parable the dogmatic truth of the Judgment: at the end of time God will judge men and separate the good from the bad. It is interesting to note our Lord's repeated references to the last things, especially Judgment and Hell: He emphasizes these truths because of man's great tendency to forget them: "All these things are said to make sure that no one can make the excuse that he does not know about them: this excuse would be valid only if eternal punishment were spoken about in ambiguous terms" (St. Gregory the Great, "In Evangelia Homilae", 11).
52. "Scribe": among the Jews a scribe was a religious teacher, a specialist in sacred Scripture and its application to life. Our Lord here uses this word to refer to the Apostles, who will have the role of teachers in His Church. Thus, the Apostles and their successors, the Bishops, are the "Ecclesia docens", the teaching Church; they have the authority and the mission to teach. The Pope and the Bishops exercise this authority directly and are also helped in this by priests. The other members of the Church form the "Ecclesia discens", the learning Church. However, every disciple of Christ, every Christian who has received Christ's teaching, has a duty to pass this teaching on to others, in language they can understand; therefore, he should make sure he has a good grasp of Christian doctrine. The treasure of Revelation is so rich that it can provide teaching which applies to all times and situations. It is for the word of God to enlighten all ages and situations--not the other way around. Therefore, the Church and its pastors preach, not new things, but a single unchanging truth contained in the treasure of Revelation: for the past two thousand years the Gospel has always been "good news".
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.