Q: How does the leniency of “cholov stam” work?
A: Chazal prohibited all milk unless witnessed by a Yisroel, who must ensure that the milk is only from kosher species (Avodah Zarah 35b, Yoreh Deah 115:1). However, there is a halachic principle of Anan Sahadei (virtual witnesses), which means that if we know that something is occurring, our clear knowledge of this occurrence is the halachic equivalent of being witnesses to it.
The heter of cholov stam, as formulated by Rav Moshe Feinstein (Igros Moshe YD 1:47-49), is predicated upon our clear knowledge that the government is properly regulating the dairy industry, including the government’s ensuring that milk from non-kosher species is not present. We know that the milk suppliers adhere to the dairy regulations because the suppliers are apprehensive of being penalized for violation and of their reputations being ruined through noncompliance. Halachah considers our clear knowledge that the milk is not from non-kosher species to be the equivalent of us being witnesses. Hence, the requirement that a Yisroel must witness all milking is fulfilled, as we are all deemed halachic witnesses to the milk’s production.
This column comes from OU Kosher’s Halacha Yomis dedicated in memory of Rav Chaim Yisroel ben Reb Dov HaLevy Belsky, zt’l, Senior OU Kosher Halachic Consultant (1987-2016). Subscribers can also ask their own questions on Kashrus issues and send them to email@example.com. These questions and their answers may be selected to become one of the Q and A’s on OU Kosher Halacha Yomis.