Psalm 78 (77 in the Septuagint and Vulgate numbering) is a long historical psalm, often called a “maskil” or instructional psalm. It is anonymous, though ancient tradition sometimes links it to Asaph. Scholars date it to the post-exilic period (perhaps 5th–4th century BC), though it draws on earlier traditions. The psalm recounts Israel’s history from the Exodus through the wilderness wanderings and settlement in the land, using it as a cautionary tale. It contrasts God’s faithful deeds with Israel’s repeated unfaithfulness, aiming to teach future generations to remember and obey. Its length and didactic style suggest it was used in Temple liturgy or communal instruction to reinforce covenant fidelity.

The selected verses (1-2, 34-35, 36-37, 38) with the response “Never forget the deeds of the Lord!” form a concentrated summary of the psalm’s message. The psalmist calls the people to listen to teaching and parables drawn from the past. He recalls how, after punishment, the people sought God and remembered Him as their rock and redeemer. Yet their repentance was superficial—they deceived Him with their mouths and were not steadfast in their hearts or faithful to the covenant. The psalm concludes with hope in God’s compassion: “Yet he who is full of compassion forgave them their sin and spared them. So often he held back his anger, and did not stir up all his rage.” This creates a powerful contrast between human fickleness and divine mercy.

In the Lectionary, these verses are appointed as the Responsorial Psalm for the Feast of The Exaltation of the Holy Cross (14 September). The feast commemorates the finding of the True Cross by St Helena and celebrates the triumph of Christ’s saving death. The First Reading (Numbers 21:4b-9) recounts the bronze serpent lifted up in the wilderness for healing; the Second Reading (Philippians 2:6-11) presents the hymn of Christ’s kenosis and exaltation; and the Gospel (John 3:13-17) links the serpent to the Son of Man lifted up on the Cross, so that all who believe may have eternal life.

The psalm fits the feast profoundly. Israel’s pattern of rebellion, punishment, repentance, and God’s repeated forgiveness foreshadows humanity’s need for salvation. The bronze serpent in Numbers becomes a type of the Cross, where Christ, lifted up, brings healing and forgiveness. The psalm’s emphasis on remembering God’s deeds and His merciful restraint points to the ultimate act of divine compassion on Calvary. For the assembly, the psalm transforms the feast into a call to remember the Cross not as defeat but as the supreme revelation of God’s mercy. The response “Never forget the deeds of the Lord!” urges the faithful to look upon the Crucified One with faith, trusting in the forgiveness won for us. In this way, the psalm invites the Church to respond to the Cross with steadfast hearts, faithful to the new covenant sealed in Christ’s blood.