Mercy is the most lovable of all virtues; it is a quality of [the Divine itself]. True mercy is love yearning over those who are in distress. Misery calls forth mercy. If one does not enjoy seeing mercy exercised towards their enemy, they have no love of mercy. If the misfortunes of an enemy give secret delight, pity for a friend in distress is not mercy. 

Mercy is no respecter of persons. The mercy of mere friendship is unmercifulness. "Such mercy sometimes appears with the evil who are in no charity; but it is grief on account of what they themselves suffer. This mercy is not the mercy of love; but it is the mercy of friendship for the sake of self, which, regarded in itself, is unmercifulness; for it despises or hates all except the friends who make one with itself." (Swedenborg, Secrets of Heaven 5132) 

When a calamity befalls someone who has done you an injury, how does it affect you? Which emotion do you detect first, distress or delight? 

"Those who bestow but a little mercy, from the heart, during the life of the body, in the other life receive unspeakable happiness; through the mercy which they possess there inflows an abundance of heavenly joy and blessedness." Our mercy toward others is the measure by which the joy and blessedness of heaven shall be given unto us. "With what measure you make, it shall be measured unto you." 

The Lord wept over Jerusalem, which represents love grieving over the unfortunate. Because the world is in a state of misery, God's love toward it is pure mercy. "His tender mercies are over all His works." The greater the misery, the greater the mercy, as long as the misery lasts, the mercy endures. 

The angels of the highest heaven are objects of God's mercy. If the states of angels excite Divine pity, what must the miseries of the unfortunate in hell do. [God's] mercy relieves the distress of those who are being tormented [by] evil lusts. In pity, the Lord saves us from ourselves, and from one another, bestowing upon us as much happiness as possible. 

Mercy cannot be indifferent to any who are in need of aid. Infinite mercy is doing all that can be done for everyone. The door of God's mercy stands open to all, and never is closed against any. This is the mercy that the Lord requires us to love. Sad, indeed, is the state of the one who does not love such mercy. "The Lord is kind to the unthankful and to the evil. Be  therefore, merciful, just as your Father also is merciful." (Luke 6:35, 36)