Psalm 138 (137 in the Septuagint and Vulgate numbering) is a joyful individual thanksgiving psalm that expresses gratitude for God’s faithful help in a time of trouble. It is traditionally attributed to David. Scholars generally date it to the post-exilic period (5th–4th century BC), when the restored community in Jerusalem reflected on God’s continuing faithfulness amid ongoing challenges. The psalm blends personal testimony with universal praise, reflecting a mature faith that sees God’s mercy extending beyond Israel. Its structure moves from personal thanks in the Temple to confidence in God’s care for the lowly, ending with a prayer of trust.

The selected verses (1-2a, 2bc-3, 6, 8bc) with the response “O Lord, your merciful love is eternal; discard not the work of your hands” form a heartfelt song of praise and petition. The psalmist thanks the Lord with all his heart for hearing his prayer and for His merciful love and faithfulness. He praises God in the presence of the angels and bows towards the holy Temple. He recalls that on the day he called, God answered and increased the strength of his soul. The psalm acknowledges God’s exalted nature—high yet looking on the lowly—and ends with confident trust in the eternal merciful love that will not abandon the work of His hands. This creates a movement from thanksgiving to humble dependence on God’s sustaining grace.

In the Lectionary, these verses are appointed as the Responsorial Psalm for the 21st Sunday in Ordinary Time, Year A. The readings focus on God’s sovereign choice and the building of the Church. The First Reading (Isaiah 22:19-23) describes the installation of Eliakim as master of the household with authority; the Second Reading (Romans 11:33-36) marvels at the depth of God’s wisdom and knowledge; and the Gospel (Matthew 16:13-20) records Peter’s confession of Jesus as the Christ and the promise to build the Church upon him, giving him the keys of the Kingdom.

Psalm 138 resonates powerfully with these themes. The psalmist’s thanks for God’s answer and strengthening of the soul parallels Peter’s confession and the divine revelation that enabled it. The confidence that God will not discard the work of His hands echoes the promise to build and sustain the Church. For the assembly, the psalm strengthens faith in God’s merciful love amid the “ordinary” challenges of Christian life. It reminds believers that the same God who chose Peter and builds the Church continues to hear prayers, strengthen souls, and accomplish His purposes. The response becomes a prayer of trust for the Church and for each believer, confident that God’s eternal merciful love will complete the good work He has begun. In this way, Psalm 138 invites the faithful to thank God with all their heart and to rely on His faithfulness.