How Did Noah Know Which Animals Were Clean?
Three biblical theories - and what they tell us about revelation, worship, and the mystery of faith.
Clean and Unclean Animals in Genesis 7:2–3
In Genesis 7:2–3, God tells Noah to take seven pairs of every clean animal and one pair of every unclean. Simple enough.. until you realize the Bible doesn’t actually define those categories until Leviticus 11 and Deuteronomy 14. So how could Noah have possibly known the difference?
That question has kept interpreters busy for centuries. Scholars have generally landed in three main camps:
Noah knew the distinction because God had already revealed it before Sinai.
The terms “clean” and “unclean” are later editorial insertions by priestly scribes.
Noah participated in the broader ancient Near Eastern practice of sacrifice, and later Israelite writers described it using familiar Mosaic categories.
Each of these positions sees something important in the text, and each raises its own set of questions.
Position 1: Noah Knew God’s Law Before Sinai
This view takes the story as written: Noah already knew which animals were “clean” because God had revealed these distinctions well before the formal giving of the Law at Sinai. In this understanding, the divine standard for acceptable sacrifice didn’t begin with Moses; it was already known to the faithful.
Evidence and Reasoning
Abel’s offering in Genesis 4 was accepted while Cain’s was not, which some interpreters take to imply that certain kinds of offerings were more pleasing to God, though the text itself doesn’t mention clean or unclean categories.
Others argue that the acceptance of Abel’s offering in Genesis 4 had less to do with clean/unclean categories and more to do with the quality and intent behind the gift. Abel offered the firstborn of his flock, an intentional and costly act, whereas Cain merely brought some of his produce. This anticipates the later biblical principle of offering God the first and best (‘first fruits’), which may better explain why Abel’s sacrifice was favored.
In Genesis 8:20, Noah offers “clean” animals after the flood, suggesting he already understood which animals were acceptable for sacrifice.
The patriarchs: Abraham, Isaac, and Jacob. Also make sacrifices later in Genesis without receiving any detailed instructions in the text.
Together, these examples suggest that God’s standards for worship were already known, even if they weren’t yet written down.
Scholarly Support
Gordon Wenham, in his Word Biblical Commentary: Genesis 1–15, writes:
“The distinction between clean and unclean animals is presupposed here, though the laws defining them were not given until Sinai. It may be that such distinctions were already known in the patriarchal period, for sacrificial animals were in fact drawn from the clean category.”
Kenneth Mathews, in The New American Commentary: Genesis 1–11:26, adds:
“Although the Levitical laws had not yet been given, the principle of sacrificial purity was already known and operative in the patriarchal period.”
Strengths: This view preserves continuity in God’s standards and the unity of Scripture across different eras.
Weaknesses: The text never explicitly says that God explained these categories to Noah, and it risks reading Mosaic law back into a much earlier period.
Position 2: Scribal Retrojection by Priestly Editors
The second view, common in critical scholarship, argues that Noah could not have known these categories at all. Instead, the terminology of “clean” and “unclean” reflects later priestly concerns, ideas and language projected backward into the Noah story by scribes familiar with Israel’s temple system.
Evidence and Reasoning
Genesis contains several examples where later ideas or names appear in earlier settings. For instance, Genesis 14:14 refers to “Dan,” a city that did not exist by that name until Judges 18. Similarly, Genesis 36:31 mentions “kings in Israel” long before Israel had a monarchy. In this pattern, the “clean/unclean” language in Genesis 7 looks like another case of editorial updating, where priestly writers wove their theological vocabulary into an older narrative.
Scholarly Support
Richard Elliott Friedman, in The Bible with Sources Revealed, explains:
“The mention of clean and unclean animals in Genesis 7 is a clear indicator of the Priestly source. This reflects the priestly concern with purity laws and sacrifices, retrojected back into the primeval history.”
Claus Westermann, in Genesis 1–11: A Commentary, notes:
“The distinction between clean and unclean, taken up here for the first time, belongs to a much later stage in Israelite religion. Its occurrence in the Noah story is best understood as an addition from priestly hands.”
Julius Wellhausen, in Prolegomena to the History of Israel, famously argued:
“The laws of clean and unclean are part of the priestly system imposed back upon the pre-Mosaic age, giving the appearance of primeval antiquity to what is in fact a later development.”
Strengths: This view explains the apparent anachronism clearly and fits with other examples of priestly editing in Genesis.
Weaknesses: It can underplay how much earlier sacrificial traditions may have shaped priestly language, rather than being purely the product of later invention.
Position 3: Cultural Practice and Scribal Updating
The third view tries to balance historical realism with theological interpretation. It argues that sacrifice was already a widespread religious practice in the ancient Near East, Noah didn’t need a Levitical code to know how to make an offering. However, when the story was written or edited for Israel, the scribes used their own categories: “clean” and “unclean” to describe what Noah did.
Evidence and Reasoning
Across the ancient Near East, in Mesopotamia, Canaan, and Egypt, sacrifice was the central act of worship. Genesis 4 assumes this cultural background when Cain and Abel bring offerings without explanation.
Noah’s sacrifice after the flood (Genesis 8:20) fits the same pattern. It even parallels the flood narratives of Mesopotamia: in The Epic of Gilgamesh (tablet XI), Utnapishtim builds an altar after the flood and the gods “gather like flies” around the sacrifice. Genesis keeps the structure but redirects the focus: only Yahweh receives the offering.
When later Israelite writers recorded or preserved this story, they naturally used the vocabulary of their own religious world to describe it. Just as Genesis 14 refers to the city of “Dan” before that name historically existed, the use of “clean” and “unclean” in Genesis 7 helps readers understand the story in familiar categories.
Scholarly Support
John Walton, in The NIV Application Commentary: Genesis, explains:
“The distinction of clean and unclean animals is introduced here without explanation, because the author assumes his audience is familiar with the categories. The fact that such terminology is used does not necessarily mean Noah had the full Mosaic law; it may simply be the narrator’s way of describing which animals were suitable for sacrifice.”
Michael Heiser, in The Unseen Realm, writes:
“Genesis sometimes uses later terminology to describe earlier events (for example, the ‘Dan’ reference in Gen 14). That doesn’t mean the events didn’t happen, only that the scribes used familiar categories. Noah may not have had a list like in Leviticus 11, but he would have known which animals were acceptable to God for sacrifice.”
Bruce Waltke, in Genesis: A Commentary, adds:
“The author interprets Noah’s actions through the lens of later categories of clean and unclean. Noah would have understood that certain animals were acceptable for sacrifice, but the terminology used in Genesis reflects Israel’s priestly vocabulary.”
Strengths: This approach preserves the historical realism of the story and recognizes Israel’s later theological framing of it.
Weaknesses: It assumes some level of scribal updating, which traditional readers may resist, and “clean” in Genesis may not line up perfectly with later Mosaic distinctions between dietary and sacrificial cleanness.
Conclusion
So, did Noah actually “know the law”? The answer depends on which lens you use.
Conservative interpreters say yes: God revealed the distinctions before Sinai, and Noah acted in obedience to divine instruction.
Critical scholars say no: the “clean/unclean” language is a later priestly addition.
Middle-ground scholars say: Noah knew how to sacrifice in his cultural context, and later writers described it in the language of Israel’s law.
The middle-ground approach is often the most satisfying. It takes the ancient Near Eastern world seriously, acknowledges that God was guiding humanity’s understanding of worship long before Sinai, and explains why Mosaic terminology appears in a pre-Mosaic story.
In that sense, Noah’s sacrifice is both ancient and theological, rooted in his world but retold in a way that made sense for Israel and, later, for readers trying to understand how the story of faith has always unfolded in conversation between God, humanity, and history itself.
Thought to Take Away
Maybe the question of whether Noah knew the law isn’t meant to be solved so much as sat with. The story invites us into mystery, a space where revelation, tradition, and human understanding overlap. Noah acts without a written law, yet his obedience fits perfectly into the story that will one day shape Israel’s worship. Was he following divine instruction long forgotten? An inherited way of sacrifice shared across cultures? Or did later writers simply give ancient devotion a familiar vocabulary?
The text doesn’t tell us, and maybe that’s the point. Genesis leaves room for wonder; for the sense that God’s relationship with humanity has always been unfolding in ways bigger than one set of rules or categories.
Perhaps the story’s real challenge is not to decide what Noah knew, but to ask what we might still have to learn.
And maybe, like Noah, faith begins not with perfect understanding, but with the courage to act on what little we know.
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Disclaimer: This post was sharpened with the help of AI tools for clarity and flow.
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