The Church celebrates today the Optional Memorial of Saint Teresa of Calcutta, whose liturgical celebration was inscribed in the General Roman Calendar by Pope Francis in December 2024 and is observed each year on September 5. For this memorial, the Holy See recommends Isaiah 58:6–11, Psalm 34, and Matthew 25:31–46, readings that beautifully illuminate Saint Teresa’s vocation to serve Christ in the poorest and most vulnerable.

 The first reading teaches that authentic worship cannot be separated from justice, mercy, generosity, and concrete care for those who suffer. Isaiah presents fasting not simply as abstaining from food but as a conversion of life that loosens oppression, feeds the hungry, shelters the homeless, and responds compassionately to human need. The Gospel brings this teaching to its fullest revelation in Christ’s teaching about the final judgment: acts of mercy toward the hungry, thirsty, stranger, naked, sick, and imprisoned are received by Christ as acts done to him. The theological center of these readings is therefore the mystery of Christ present in those who suffer and the inseparability of love of God from love of neighbour. This does not mean that Christian charity is merely humanitarian service; rather, supernatural charity flows from communion with Christ and recognizes his image and dignity in every human person (CCC 1700, 1931–1933, 2443–2449). Saint Teresa’s life offers a particularly striking witness to this truth. Her service was rooted in prayer, the Eucharist, religious consecration, and a profound desire to respond to Christ’s thirst for souls. The Church’s celebration of her memorial consequently calls us beyond sentimentality toward conversion: to allow Christ’s love to become concrete through mercy, sacrifice, generosity, and faithful service to those whom the world may overlook.

Isaiah’s prophetic teaching challenges every attempt to separate religious devotion from the moral demands of charity. The people of God are called to worship with lives that reflect God’s own justice and mercy. This theme runs throughout Scripture. Deuteronomy 15:7–11 commands generosity toward the poor; Proverbs 19:17 teaches that generosity to the needy is remembered by God; and James 2:14–17 insists that faith cannot remain indifferent when a brother or sister is in material need. Yet Catholic teaching avoids reducing these passages to a merely social ethic. The human person possesses an inviolable dignity because every person is created in the image and likeness of God (Genesis 1:26–27), and Christ has united himself in some fashion with every human being through his Incarnation (CCC 1700, 1934–1935). Consequently, works of mercy are not optional decorations added to Christian life; they belong to the concrete exercise of charity. The Catechism teaches that the corporal works of mercy—feeding the hungry, giving drink to the thirsty, sheltering the homeless, visiting the sick and imprisoned, and caring for the needy—express love of neighbour and respond to Christ’s command (CCC 2447). Isaiah’s promise that God will guide, strengthen, and renew those who practice such justice also reveals that authentic charity becomes itself a path of sanctification. When Christians give themselves generously, they discover that divine grace does not diminish human freedom but elevates and perfects it, enabling the believer to participate in God’s own love (CCC 1996–2001).

The Gospel of Matthew gives these works of mercy their deepest Christological meaning. The Son of Man comes in glory as judge, and the decisive question concerns the way people have responded to those who were hungry, thirsty, strangers, naked, sick, or imprisoned. Christ identifies himself so closely with “the least” that love shown to them becomes love shown to him. This teaching must be read together with Matthew 22:37–40, where love of God and love of neighbour are inseparably joined, and with John 13:34–35, where Christ makes self-giving love the distinguishing mark of his disciples. The Church therefore sees the corporal and spiritual works of mercy as expressions of Christian charity rather than substitutes for faith, worship, or sacramental life (CCC 1822–1829, 2447). Saint Teresa of Calcutta’s vocation exemplified this integration. She did not see the suffering person merely as someone requiring material assistance; she sought to encounter and serve Christ in that person. Her vocation was sustained by the Eucharist and by prayer, and the proper Collect for her memorial explicitly recalls her response to Christ’s thirst on the Cross and her service to the poorest of the poor.

Her witness also reminds us that Christian charity involves the whole person. The Church defends human dignity from conception to natural death and calls Christians to work for justice while personally practicing compassion, forgiveness, generosity, and solidarity (CCC 1928–1942, 2258–2279). Mercy must therefore become visible in our homes, workplaces, parishes, communities, and relationships.

Today’s liturgy ultimately invites us to ask whether our love for Christ has become tangible in the way we treat those who need us. Saint Teresa’s example teaches that holiness is not ordinarily achieved through spectacular deeds but through faithful love offered to Christ in the ordinary people and difficult circumstances placed before us. Psalm 34:2–3, 4–5, 6–7, 8–9, 10–11 directs the heart toward continual praise and confidence in the Lord, reminding us that mercy begins in gratitude for God’s own goodness. Christ himself is the source of this charity: through Baptism we are incorporated into him, through the Sacrament of Reconciliation we are restored when sin has wounded charity, and through the Eucharist we receive the very Christ whom we are called to recognize and serve in others (CCC 1265–1270, 1422–1424, 1324, 1391–1397). The Eucharist is therefore never detached from the works of mercy; communion with Christ sends us outward in love. As 1 John 4:7–12 teaches, love of neighbour flows from God’s prior love for us. Saint Teresa’s life gives concrete witness to this Eucharistic logic: receive Christ, remain with Christ, and serve Christ in the suffering neighbour. May today’s celebration move us from admiration to imitation, from compassion in thought to mercy in action, and from external religious practice to a heart transformed by divine charity. In serving Christ in the least, we discover that the Lord we seek in prayer and sacrament is already waiting for us in the person who needs our love.