Peter Chrysologus writes: “Fasting is the soul of prayer, mercy is the lifeblood
of fasting. So if you pray, fast; if you fast, show mercy; if you want your
petition to be heard, hear the petition of others. If you do not close your ear
to others, you open God’s ear to yourself” (Sermo 43: PL 52, 320. 322).

Quoted in the pope's Lent message.