An extract from 'The Second Word: The Lesson of Mercy' in Fulton Sheen's book, The Cross and the Beatitudes: Lessons on Love and Forgiveness:
"THE BEATITUDE of the world... runs like this: "Blessed is the man who thinks first about himself." Life for the world is a struggle for existence in which victory belongs only to the egotists. Liberality, generosity, and graciousness are rare. How often the world insists on 'rights', how rarely does it emphasize 'duties'; how often it uses the possessive 'mine', and how rarely the generous 'thine'. How full it is of 'courts of justice', but how few are its 'courts of mercy'.
"Our Lord came to correct such an exaggerated justice which knew no mercy. Mercy, he reminded us, was something more than a sentimental, emotional tender-heartedness. The very word mercy is derived from the Latin miserum cor, a sorrowful heart. Mercy is, therefore, a compassionate understanding of another's unhappiness.
"A person is merciful when he feels the sorrow and misery of another as if it were his own. Disliking misery and unhappiness, the merciful person seeks to dispel the misery of his neighbour just as much as he would if the misery were his own. That is why, whenever mercy is confronted not only with pain, but with sin and wrong-doing, it becomes forgiveness which not merely pardons, but even rebuilds into justice, repentance, and love."
"Blessed are the merciful, for they will receive mercy." -- Matthew 5:7
"He replied, 'Truly I tell you, today you will be with me in Paradise.' " -- Luke 23:43
"MERCY is one of the dominant notes in the preaching of our Lord. His parables were parables of mercy. Take for example the hundred sheep, the ten pieces of money, and the two sons. Of the hundred sheep, one was lost, of the ten pieces of money, one was lost; of the two sons, one led a life of dissipation.... All these illustrations Our Lord followed with the simply truth: "There shall be more joy in heaven upon one sinner that does penance than upon ninety-nine just who need not do penance."
"... Some were scandalized at him because he 'dined with the publicans and sinners', but he never ceased to remind us that we should be merciful because the heavenly Father was merciful.... That is why he was merciful to Magdalen, to the woman at the weel, to Peter who denied him, to Zacchaeus, and even to Judas whom he addressed as 'friend'.
"There was no mistaking his point of view; he was interested in sinners not because of their merits, but because of their misery. And now at the close of his life, he fulfills the Beatitude of Mercy in his second word from the Cross.
"There were three crosses on Calvary: the crosses of two theieves and the Cross of the Good Shepherd. Of the three who hung silhouetted against that blackened sky, one was selfish and thought only of himself -- that was the thief on the left. He was interested neither in the Savior who suffered patiently nor in the thief who begged for mercy. He had no thought but for himself as he addressed the Man on the central cross: "If you be Christ, save yourself and us."
"The thief on the right, on the contrary, thought not of himself, but about others, namely the thief on the left and Our Blessed Lord. His compassion went out to the thief on the left, because he was not turning to God in this last hour of his life and begging for forgiveness: "Neither do you fear God, seeing you are under the same condemnation." He also thought of the meek Man crucified between the two of them, who had just prayed for his executioners and was innocent and good: "We indeed (suffer) justly, for we receive the due reward of our deeds; but this man has done no evil."
"It is interesting to inquire why the merciful Savior not only forgave the penitent thief, but even gave him the Divine Promise: "This day you shall be with me in paradise." Why did not Our Lord address the same words to the the thief on the left? The answer is to be found in the Beatitude of Mercy: "Blessed are the merciful: for they shall obtain mercy." [wow!]
"Because the thief on the right was merciful and compassionate, he received mercy and compassion. Because he was thoughtless of self, someone thought of him. There is a law about mercy just as rigid as the laws of nature. What we sow that also we reap. If we sow sparingly we reap sparingly. If we sow generously, we reap an abundant harvest. Raised to a spiritual level, this means, as Our Lord has said, "For with what judgment you judge, you shall be judged; and with what measure you mete, it shall be measured to you again."
"... Unless we throw something up, nothing will come down; unless there is an action there can never be a reaction; unless we give, it shall not be given to us; unless we love, we shall not be loved; unless we pardon evil, our evil shall not be forgiven; unless we are merciful to others, God cannot be merciful to us.
"If our heart is filled with the sand of our ego, how can God fill it with the fire of his Sacred Heart? If there is no 'for sale' sign on the selfishness of our souls, how can God take possession of them?
"... When therefore you are on a cross of pain or sorrow always think of that cross as the cross of the thief on the right. As such, let your prayers go out to those on the left cross that they may be mindful of the expiatory value of their suffering; let your love also go out to the Good Shepherd on the central Cross who suffers so innocently for all people, and because you never once thought of yourself but of others, or in other words, because you were merciful, you will hear the reward of mercy from the central Cross: "This day you shall be with me in paradise." In that way you become another Good Thief, for a Good Thief is one who steals Paradise!"