The love and mercy of God towards sinners. We need to rejoice with the Father at the return of his prodigal sons of his sons and daughters to the Church. We need to learn to be merciful towards the weaknesses and failings of others. We who are strong ought to put up with the failings of the weak.
Rejoice, Jerusalem, and all who love her. Be joyful, all who were in mourning; exult and be satisfied at her consoling breast. Cf. Is 66.10-11