From: Matthew 25:31-46
The Last Judgment
 "When the Son of Man comes in His glory, and all the angels with Him, then He will sit on His glorious throne.  Before Him will be gathered all the nations, and He will separate them one from another as a shepherd separates the sheep from the goats,  and He will place the sheep at His right hand, but the goats at the left.  Then the King will say to those at His right hand, `Come, O blessed of My Father, inherit the Kingdom prepared for you from the foundation of the world;  for I was hungry and you gave Me food, I was thirsty and you gave Me drink, I was a stranger and you welcomed Me,  I was naked and you clothed Me, I was sick and you visited Me, I was in prison and you came to Me.'  Then the righteous will answer Him, `Lord, when did we see Thee hungry and feed thee, or thirsty and give thee drink?  And when did we see Thee a stranger and welcome Thee, or naked and clothe Thee?  And when did we see Thee sick or in prison and visit Thee?'  And the King will answer them, `Truly I say to you, as you did it to one of the least of My brethren, you did it to Me.'  Then He will say to those at His left hand, `Depart from Me, you cursed, into the eternal fire prepared for the devil and his angels;  for I was hungry and you gave Me no food; I was thirsty and you gave Me no drink,  I was a stranger and you did not welcome Me, naked and you did not clothe Me, sick and in prison and you did not visit Me.'  Then they also will answer, `Lord, when did we see Thee hungry or thirsty or a stranger or naked or sick or in prison, and did not minister to Thee?'  Then He will answer them, `Truly, I say to you, as you did it not to one of the least of these, you did it not to Me.'  And they will go away into eternal punishment, but the righteous into eternal life."
31-46. The three parables (Matthew 24:42-51; 25:1-13; and 25:14-30) are completed by the announcement of a rigorous last judgment, a last act in a drama, in which all matters of justice are resolved. Christian tradition calls it the Last Judgment, to distinguish it from the "Particular Judgment" which everyone undergoes immediately after death. The sentence pronounced at the end of time will simply be a public, formal confirmation of that already passed on the good and the evil, the elect and the reprobate.
31-33. In the Prophets and in the Book of Revelation the Messiah is depicted on a throne, like a judge. This is how Jesus will come at the end of the world, to judge the living and the dead.
The Last Judgment is a truth spelled out in the very earliest credal statements of the Church and dogma of faith solemnly defined by Benedict XII in the Constitution "Benedictus Deus" (29 January 1336).
35-46. All the various things listed in this passage (giving people food and drink, clothing them, visiting them) become works of Christian charity when the person doing them sees Christ in these "least" of His brethren.
Here we can see the seriousness of sins of omission. Failure to do something which one should do means leaving Christ unattended.
"We must learn to recognize Christ when He comes out to meet us in our brothers, the people around us. No human life is ever isolated. It is bound up with other lives. No man or woman is a single verse; we all make up one divine poem which God writes with the cooperation of our freedom" ([St] J. Escriva, "Christ Is Passing By", 111).
We will be judged on the degree and quality of our love (cf. St. John of the Cross, "Spiritual Sentences and Maxims", 57). Our Lord will ask us to account not only for the evil we have done but also for the good we have omitted. We can see that sins of omission are a very serious matter and that the basis of love of neighbor is Christ's presence in the least of our brothers and sisters.
St. Teresa of Avila writes: "Here the Lord asks only two things of us: love for His Majesty and love of our neighbor. It is for these two virtues that we must strive, and if we attain them perfectly we are doing His will [...]. The surest sign that we are keeping these two commandments is, I think, that we should really be loving our neighbor; for we cannot be sure if we are loving God, although we may have good reasons for believing that we are, but we can know quite well if we are loving our neighbor. And be certain that, the farther advanced you find you are in this, the greater the love you will have for God; for so dearly does His Majesty love us that He will reward our love for our neighbor by increasing the love which we bear to Himself, and that in a thousand ways: this I cannot doubt" ("Interior Castle", V, 3).
This parable clearly shows that Christianity cannot be reduced to a kind of agency for "doing good". Service of our neighbor acquires supernatural value when it is done out of love for Christ, when we see Christ in the person in need. This is why St. Paul asserts that "if I give away all I have...but have not love, I gain nothing" (1 Corinthians 13:3). Any interpretation of Jesus' teaching on the Last Judgment would be wide of the mark if it gave it a materialistic meaning or confused mere philanthropy with genuine Christian charity.
40-45. In describing the exigencies of Christian charity which gives meaning to "social aid", the Second Vatican Council says: "Wishing to come to topics that are practical and of some urgency, the Council lays stress on respect for the human person: everyone should look upon his neighbor (without any exception) as another self, bearing in mind, above all, his life and the means necessary for living it in a dignified way, `lest he follow the example of the rich man who ignored Lazarus, the poor man' (cf. Luke 16:18-31).
"Today there is an inescapable duty to make ourselves the neighbor of every man, no matter who he is, and if we meet him, to come to his aid in a positive way, whether he is an aged person abandoned by all, a foreign worker despised without reason, a refugee, an illegitimate child wrongly suffering for a sin he did not commit, or a starving human being who awakens our conscience by calling to mind the words of Christ: `As you did it to one of the least of these My brethren, you did it to Me.'" ("Gaudium Et Spes," 27).
46. The eternal punishment of the reprobate and the eternal reward of the elect are a dogma of faith solemnly defined by the Magisterium of the Church in the Fourth Lateran Council (1215): "He [Christ] will come at the end of the world; He will judge the living and the dead; and He will reward all, both the lost and the elect, according to their works. And all these will rise with their own bodies which they now have so that they may receive according to their works, whether good or bad; the wicked, a perpetual punishment with the devil; the good, eternal glory with Christ."
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.