Catholic Commentary
The Writing of the Covenant and Moses' Forty Days on Sinai
27Yahweh said to Moses, “Write these words; for in accordance with these words I have made a covenant with you and with Israel.”28He was there with Yahweh forty days and forty nights; he neither ate bread, nor drank water. He wrote on the tablets the words of the covenant, the ten commandments.
Exodus 34:27–28 records God commanding Moses to write the covenant terms, the Ten Commandments, which reaffirm the broken Sinai covenant. Moses fasts for forty days while writing the tablets, sustained entirely by divine presence rather than physical nourishment.
God writes the covenant twice—once by His own hand, once through Moses—because mercy demands that sinners receive the same law all over again.
Catholic tradition illuminates this passage at several levels simultaneously.
Covenant renewal as a type of Confession and Mercy. The second set of tablets, written after Israel's sin, is a paradigmatic image of divine mercy restoring what human sin has shattered. St. John Chrysostom noted that the second covenant is in some ways more magnificent than the first precisely because it is given to sinners — it is a covenant of re-creation. This typology runs forward into the Sacrament of Penance. The Catechism (§1486) calls Reconciliation a "second conversion," an echo of Israel's second covenant. Just as Moses interceded for Israel and obtained renewed communion, Christ the one Mediator (1 Tim 2:5) intercedes for sinners and restores the covenant sealed in His blood.
Moses as type of Christ. The Church Fathers, particularly Origen (Homilies on Exodus) and St. Gregory of Nyssa (Life of Moses), read Moses' ascent of Sinai, his fasting, his mediatorial role, and his radiant face (34:29–35) as figures of Christ's own intimacy with the Father. Moses' forty-day fast directly prefigures Christ's forty days in the desert (Matt 4:2), and both Luke (9:31) and the Transfiguration narrative reinforce this Moses–Christ typology explicitly.
Scripture and Tradition. The writing command in v.27 is theologically important for Catholic teaching on revelation. Dei Verbum §9 teaches that Sacred Scripture and Sacred Tradition together form one sacred deposit of the Word of God. The act of writing here is not the exhaustion of revelation but the beginning of its transmission — Tradition carries what the written text alone cannot contain.
The Decalogue in Catholic moral theology. The Catechism (§§2052–2082) structures its entire treatment of the moral life around the Ten Commandments, affirming with Exodus 34:28 that they constitute the irreducible grammar of covenant life. Vatican II's Gaudium et Spes (§89) reaffirms that the natural moral law and the revealed Decalogue converge, pointing to the universal moral order inscribed on the human heart and confirmed on Sinai's tablets.
Contemporary Catholics live in a culture that is deeply ambivalent about the very concept of binding moral law, and Exodus 34:27–28 speaks pointedly into that ambivalence. The Ten Commandments are not a burden imposed on free persons but — as the text's own framing insists — the words of a God who has already liberated His people. They are covenant language, the vocabulary of an intimate relationship, not the bylaws of a cosmic bureaucrat.
Moses' total fast also invites reflection on what it means to be truly present to God in prayer. He "neither ate bread nor drank water" — he was not multitasking. For many Catholics, prayer has been reduced to brief petitions squeezed between competing demands. The image of Moses, sustained for forty days by nothing except the presence of Yahweh, challenges us to take seriously extended, undistracted time in God's presence: longer Eucharistic adoration, annual retreats, fasting as a spiritual discipline rather than merely a penitential one.
Finally, the context of renewal after sin is pastorally crucial. The second tablets are given to people who had just worshipped a golden calf. No Catholic should read this passage and conclude that their sin has placed them beyond the reach of covenant. The writing of these words is itself the record of God's unwillingness to abandon His people.
Commentary
Exodus 34:27 — "Write these words; for in accordance with these words I have made a covenant with you and with Israel."
The imperative "write" (Hebrew: kātab) carries enormous weight in the Sinai narrative. Writing is not mere documentation; in the ancient Near East, the written word sealed treaties and made them legally binding across generations. God had previously written on the first tablets Himself (Exod 31:18; 32:16), but here, in a significant literary and theological detail, Moses is commanded to write. This is not a contradiction of Deut 10:2, where God again writes on the second tablets — the text invites us to see a collaboration: the divine Word is committed to human hands and human language without being diminished. This foreshadows the entire dynamic of Sacred Scripture as the Church understands it: God as primary author, the human writer as genuine secondary author (Dei Verbum §11).
The phrase "in accordance with these words" ('al-pî haddebārîm hā'ēlleh) is pivotal. The covenant ratified here is not a new law but a reaffirmation of the Sinai covenant broken at the golden calf (Exod 32). That God chooses to re-covenant with a people so recently apostate is itself the theological headline. The covenant is grounded not in Israel's fidelity but in God's hesed — His steadfast, covenantal love — which has just been proclaimed in the great theophany of 34:6–7. The word "covenant" (berît) links this moment to the entire patriarchal and Mosaic covenant tradition, and the naming of both Moses and Israel as parties reflects the mediatorial role Moses has played since Exodus 32:11–14, where his intercession literally saved the nation from destruction.
Exodus 34:28 — "He was there with Yahweh forty days and forty nights; he neither ate bread, nor drank water."
This is Moses' second forty-day fast on Sinai (cf. the first in Exod 24:18; Deut 9:9). Forty days in biblical numerology is never merely chronological — it is the period of divine preparation, testing, and transformation: the flood rains (Gen 7:4), Elijah's journey to Horeb (1 Kgs 19:8), and supremely, Jesus' forty days in the desert (Matt 4:2). Moses' complete abstention from food and water signals that he is sustained entirely by the divine presence, as if the body's natural needs are suspended at the threshold of the holy. This is more than extraordinary endurance; it is a theological statement about the sufficiency of God.
"He wrote on the tablets the words of the covenant, the ten commandments ('ăśeret haddebārîm — literally 'the ten words')." The Decalogue is here identified explicitly as the condensed heart of the covenant. The Greek (from which we derive our term) and the Hebrew "ten words" both capture the same idea: that the covenant's moral architecture is comprehensive, arranged in a sacred number that is complete and ordered. These are not merely legal stipulations but the terms of an intimate relationship — the opening commandment, "I am Yahweh your God who brought you out of Egypt," is the declaration of a deliverer, not merely a lawgiver. The Catechism (§2061) accordingly teaches that the commandments are properly understood as the response of a freed people to their liberating God, not as preconditions for divine favor.