English language dictionaries are of limited help in understanding this mercy's biblical usage. In English "mercy" is normally used to mean showing compassion, forbearance, pity, sympathy, forgiveness, kindness, tenderheartedness, or liberality or refraining from harming or punishing offenders or enemies. These synonyms give us some insight on this word; they all express how a merciful person might act. However, none of them specifically pictures what biblical mercy is because the scriptural concept is virtually untranslatable into a single English word.
The Greek word used in Matthew 5:7, eleemon, means essentially the same as its English counterpart, "merciful." However, in all likelihood Jesus spoke in Aramaic, and the idea behind His statement about mercy come from Old Testament—that is, Hebrew—usage and teaching. The word He would have used is the Hebrew and Aramaic chesed.
William Barclay's Daily Study Bible commentary on Matthew states regarding this word:
It does not mean only to sympathize with a person in the popular sense of the term; it does not mean simply to feel sorry for some in trouble. Chesedh [sic], mercy, means the ability to get right inside the other person's skin until we can see things with his eyes, think things with his mind, and feel things with his feelings.
Clearly this is much more than an emotional wave of pity; clearly this demands a quite deliberate effort of the mind and of the will. It denotes a sympathy which is not given, as it were, from outside, but which comes from a deliberate identification with the other person, until we see things as he sees them, and feel things as he feels them. This is sympathy in the literal sense of the word. Sympathy is derived from two Greek words, syn which means together with, and paschein which means to experience or to suffer. Sympathy means experiencing things together with the other person, literally going through what he is going through. (p. 103)
Much easier said than done! Having a sense of another's feelings to this degree is very difficult to do because we are normally so self-concerned, so aware of our own feelings, that sensitivity for others to this depth often requires a great effort of the will. Normally, when we feel sorry for someone, it is an exclusively external act because we do not make the effort to get inside another's mind and heart until we can see and feel things as he does. It is not easy to walk in another person's shoes.
The world, from which we have all come, is true to its nature; it is unmerciful. The world prefers to insulate itself against the pains and calamities of others. It finds revenge delicious and forgiveness tame and unsatisfying.
This is where we all begin. Indeed, all too often in the church, worldliness is hardly dormant, revealing itself in acts that show some degree of cruelty. Usually, these cruelties are delivered verbally, but all too frequently, brethren simply ignore the real needs of others.
The mercy Jesus teaches is not humanly derived. He says in Matthew 6:14, "If you forgive men their trespasses, your heavenly Father also will forgive you." This occurs, not because we can merit mercy by being merciful or forgiving of others, but because we cannot receive the mercy and forgiveness of God unless we repent. We cannot claim to have repented of our sins if we are unmerciful towards the sins of others.
The truly merciful are too aware of their own sins to deal with others in sharp condemnation, so they constrain themselves to deal humbly and kindly with those in need. Nothing moves us to forgive others like the amazing realization that God has forgiven our sins. Mercy in God's children begins by experiencing His forgiveness of them, and perhaps nothing proves more convincingly that we have been forgiven than our readiness to forgive.
Recognizing God's mercy is a key element in motivating our expressions of mercy. Too many people today, even in the church, possess a "welfare mentality." They go through life with little or no gratitude, thinking they deserve the handouts of governments or private citizens. Ingratitude is vital to understanding this because, as long as one is unthankful, his thoughts will center on himself. The merciful person is sensitive to others' needs and takes action to supply them. An ungrateful person, though, insulates himself from others' pains because he is too focused on his own perceived miseries.
John W. Ritenbaugh
The Beatitudes, Part 5: Blessed Are the Merciful