Numbers 19:2 

זֹ֚את חֻקַּ֣ת הַתּוֹרָ֔ה אֲשֶׁר־צִוָּ֥ה יְהֹוָ֖ה לֵאמֹ֑ר דַּבֵּ֣ר ׀ אֶל־בְּנֵ֣י יִשְׂרָאֵ֗ל וְיִקְח֣וּ אֵלֶ֩יךָ֩ פָרָ֨ה אֲדֻמָּ֜ה תְּמִימָ֗ה אֲשֶׁ֤ר אֵֽין־בָּהּ֙ מ֔וּם אֲשֶׁ֛ר לֹא־עָלָ֥ה עָלֶ֖יהָ עֹֽל׃

This is the Statute that God has commanded: Instruct the Israelite people to bring you a red cow without blemish, in which there is no defect and on which no yoke has been laid.

On the Shabbat a few weeks before Passover we read a curious section of the Torah all about the ritual of the Red Heifer. This was a cow, entirely red, that would be offered up on the altar. Once completely burned up, the ashes were mixed with water, and that ash-water would then be used as a means to purify anyone who came into contact with a dead body. 

The big question the Rabbis ask is: Why are the ashes of a red heifer effective in taking away that extremely strong level of impurity imposed through contact with the deceased? The answer they give is: We don’t know. It’s one of the few times in our tradition that no attempt at an explanation is made. Rather, this law is set aside as one where the limits of our understanding are reached. 

“Teach your tongue to say I don’t know” we read in the Talmud. In an age where we are flush with information, saying “I don’t know” has become a lost art. This mitzvah is set aside as an eternal reminder that we don’t know everything,  that we can’t know everything, and that the words “I don’t know” are not a sign of weakness, but of humility and a recognition of our own human limitations.