Pope Francis didn’t invent the emphasis on mercy. In Evangelii Gaudium 37, he explains the notion derives from the Angelic Doctor:
37. Saint Thomas Aquinas taught that the Church’s moral teaching has its own “hierarchy”, in the virtues and in the acts which proceed from them.[Cf. S. Th., I-II, q. 66, a. 4-6] What counts above all else is “faith working through love” (Gal 5:6).
We begin looking at love, as expressed and honored by Saint Paul.
Works of love directed to one’s neighbor are the most perfect external manifestation of the interior grace of the Spirit: “The foundation of the New Law is in the grace of the Holy Spirit, who is manifested in the faith which works through love”.[S. Th., I-II, q. 108, a. 1]
Mercy was certainly not unknown to adherents to the Old Law either. Remember Micah 6:6-8, or Isaiah 58, among others–the prophetic insight that God most desires mercy. Or at the very least mercy above sacrifice.
Like worship, mercy is an external manifestation of an inner orientation toward God.
Thomas thus explains that, as far as external works are concerned, mercy is the greatest of all the virtues: “In itself mercy is the greatest of the virtues, since all the others revolve around it and, more than this, it makes up for their deficiencies. This is particular to the superior virtue, and as such it is proper to God to have mercy, through which his omnipotence is manifested to the greatest degree”.[S. Th., II-II, q. 30, a. 4] : “We do not worship God with sacrifices and exterior gifts for him, but rather for us and for our neighbor. He has no need of our sacrifices, but he does ask that these be offered by us as devotion and for the benefit of our neighbor. For him, mercy, which overcomes the defects of our devotion and sacrifice, is the sacrifice which is most pleasing, because it is mercy which above all seeks the good of one’s neighbor” (S. Th., II-II, q. 30, a. 4, ad 1).
An all-good and perfect God will be unconcerned with his own welfare, as if liturgical practices could enhance his Divinity in any way. The self-sacrificing example of Christ should give us enough inspiration on this point. Would the sacrifice of Jesus come to an end with his expiration on the cross? Doubtful, that.
Liturgy is intended to be devotion to God, not filling a need. And Thomas suggests that liturgy has a benefit for our neighbors. If so, how does that happen? It would seem that an external act (the Mass, for example) representing an inner faith and orientation to God would have a parallel in a posture of mercy, representing an inner love for others. Neighbors, yes–but strangers, too. Even the enemy.