Why the Tenth?

The mystery behind Yom Kippur’s date

A congregant asked me a question after Rosh Hashanah that I should have been able to answer. I could not. “Rabbi, why is Yom Kippur on the tenth day of the month?”

At first, the answer seemed obvious. Yom Kippur occurs on the tenth of Tishrei because the Torah says so. But that only restates the question. The more I thought about it, the stranger the date became.

Biblical festivals frequently coincide with recognizable moments in the lunar month. Yom Teruah, what we call Rosh Hashanah, occurs on the first. Passover and Sukkot arrive at mid-month, around the full moon. Shavuot is different, but there the Torah gives us a mechanism for arriving at the festival: count seven weeks, forty-nine days, and then celebrate. Yom Kippur simply appears on the tenth.

Leviticus is quite precise: “In the seventh month, on the tenth day of the month.” It tells us what the day demands. We are to afflict ourselves, refrain from work, and seek atonement. It never tells us why the tenth. Jewish tradition eventually supplied a magnificent answer.

The rabbis reconstructed the chronology of Moses’ ascents of Mount Sinai after the sin of the Golden Calf. According to Seder Olam Rabbah, Moses descended with the second tablets on the tenth of Tishrei and announced that Israel had once again found favor with God. The broken covenant had been restored. That day, the tradition teaches, became permanently associated with forgiveness and reconciliation. It is difficult to imagine a more fitting explanation for Yom Kippur. But intellectual honesty requires us to say what it is: a rabbinic interpretation. The Torah itself never connects the tenth of Tishrei with Moses’ descent from Sinai.

Then someone suggested another possibility. Could the date have roots in Egypt, the civilization from which Israel’s foundational story says we emerged? There is just enough evidence to make the question intriguing, and not nearly enough to make it history. Ancient Egyptians organized their thirty-day months into three ten-day periods. In Thebes, there was also a recurring ten-day observance in which Amun of Luxor traveled in procession toward the temple complex at Medinet Habu. Later sources refer to this complex of rites as what Egyptologists call the Decade Festival. Ten-day units, in other words, had genuine calendrical and religious significance in Egypt. But there is no evidence that Hebrew slaves witnessed an Egyptian festival on the tenth day and transformed it into Yom Kippur. The Egyptian observance recurred every ten days. It involved processions of a divine image and rites very different from the national fast and purification ritual of Leviticus. Interesting context is not proof of origin.

Then there is Babylonia. Here the comparison becomes even more intriguing. The best-documented Babylonian Akitu celebration, held in the spring month of Nisannu, unfolded over eleven days and included temple rites, purification, divine kingship and the determination of destinies for the coming year. Related New Year observances were also known in the autumn month of Tashritu, from which our name Tishrei ultimately derives. Scholars have long noticed parallels between the religious world of the Babylonian New Year and biblical ideas associated with the season of Rosh Hashanah and Yom Kippur. Earlier scholars went further, asking whether Israel’s autumn New Year complex itself developed in conversation with Mesopotamian festival traditions. The theory remains debated. Similarity does not establish borrowing, and no cuneiform tablet tells us that ancient Judeans adopted the tenth day from Babylonia and turned it into Yom Kippur.

Still another possibility comes from modern biblical scholarship. Some scholars argue that the ritual at the heart of Leviticus 16 may originally have been a sanctuary-purification ceremony performed when needed. Only later, according to this reading, was it fixed to one annual date, the tenth day of the seventh month. The fact that the date appears relatively late in the chapter is part of the argument. Other scholars disagree and read the chapter as a coherent whole. 

So after Torah, rabbinic tradition, Egypt, Babylonia and modern biblical scholarship, where does that leave us?

With a surprisingly simple answer. We know exactly when Yom Kippur occurs. We do not know with equal certainty why that particular date was chosen. And I have come to think there is something deeply appropriate about that.

Religion is often tempted to fill every silence. When the text does not explain something, we supply an explanation. When history leaves a gap, we construct a bridge. Over time, we can forget which part was ancient ground and which part was the bridge we built across it. Judaism has another sentence available to us: We do not know. That is not a failure of faith. Sometimes it is simply an expression of intellectual humility. Yom Kippur is, after all, a day devoted to acknowledging the limits of our self-knowledge. We confess sins we recognize and others we may not. We ask forgiveness for consequences we did not foresee. We stand before a God we cannot fully comprehend while examining lives we do not fully understand. Absolute certainty would be an odd posture for such a day. 

The Torah gives us the date. The rabbis give us a powerful memory of forgiveness after the Golden Calf. Egypt reminds us that ten-day units of sacred time existed in the ancient world. Babylonia places Israel within a much larger Near Eastern conversation about New Year, purification and judgment. Modern scholars remind us that biblical ritual itself has a history. And the tenth of Tishrei still keeps something to itself.

This Sunday evening, Jews throughout the world will enter Yom Kippur on exactly the day our ancestors commanded us to observe it. We may never know precisely why the tenth was chosen. But generations of Jews have known what to do when it arrives: Stop. Examine. Confess. Forgive. Return. Sometimes knowing what a sacred moment asks of us matters more than knowing exactly how that moment first became sacred.