What is mercy
The Gospel of Luke is the gospel that most teaches about Mercy, we find references to this gift in the Parable of the Good Samaritan (Luke 10: 29-37) and in the Parable of the Prodigal Son (Luke 15: 11-32). The Parables are known as the Parables of Mercy and are found only in the Gospel of Luke. These beautiful Parables (stories) are synthesized in the teaching of the Gospel of Luke:
Be merciful, just as your Father is merciful. Luke 6:36
Mercy is defined as compassion, gentleness, affability, benevolence, benedicence. The ancient Greek philosophers considered Mercy as ethical friendship, as a perfect virtue, that is, a maximum virtue in its own genre. In the Gospels the perspective of Mercy is different and it is defined as a perfection, a spiritual gift which origin is God: "Be perfect as your heavenly Father is perfect", Matthew 5:48. The Kingdom of God is the Dominion of the perfections of God, the domain of wisdom, of constancy, of continuous improvement, of mercy.
In the Parable of the Good Samaritan we find the foundation of the Mercy: "But a Samaritan, as he traveled, came where the man was, and when he saw him, he took pity on him" Luke 10:33. The base of the feeling of compassion is empathy, empathy arises when the situation of the neighbor moves, touch us in the heart. It is here that we understand that empathy among with intuition and inspiration are faculties of the spirit, that is to say of the divine substance, as Thomas Aquinas teaches.
The faculties of the mind are the base of the gifts (infused virtues) and human virtues.
In the Parable of the Prodigal Son we see the difference between Justice and Mercy. Justice is to give and receive proportionally teaches Aristotle in Nicomachean Ethics, but the mercy is to give and receive taking into account the dignity of the neighbor, or to say the other. The loyal son asks for justice, but the father, on the other hand, responds with mercy and forgiveness.
The evangelist with these important stories teaches us that Mercy is a beatitude, a blessing, a promise and an end in itself.