The Ran (1a, u’ma) suggests that the prohibition of “Bal Yira’eh…Bal Yimatze” is actually meant to protect against the violation of the prohibition of eating chametz, which is an injunction both unusually severe (carrying a penalty of karet) and unusually vulnerable (as chametz is permitted the rest of the year).

The Ran’s view is noteworthy in that it assigns “safeguard” status, which is generally associated with rabbinical enactments, to a biblical prohibition. However, as R. Yosef Engel (Lekach Tov, 8) notes, there may be many other such examples. He lists seventeen possible instances of biblical safeguards, and an independently compiled list in the Responsa Yad Sofer (#26) yields three more, while the author’s son, R. Yochanan Sofer, provides another eight in his footnotes (Ittur Soferim) to that work. (See Ketonet Yosef [Memorial Volume for R. Yosef Wanefsky], pp. 143-147).

This position may possibly affect the debated question of whether the prohibition of “Bal Yira’eh…Bal Yimatze” applies to a portion of chametz less than a “k’zayit”. The Pri Megadim (Petichah HaKollelet I, 17) suggests that the if the prohibition of eating less than a complete measurement of forbidden substances (chatzi shiur) is taken as a safeguard against eating the whole amount (a vigorously debated assumption), that it may not be combined with another safeguard, as we do not impose double safeguards (gezeirah l’gezeirah). The application of that principle to biblical safeguards is highly questionable (as R. Engel discusses, ibid, 8:2), but, if that premise is granted, the combination of “Bal Yira’eh…Bal Yimatze” and “chatzi shiur” might be affected. (The Pri Megadim himself does cite the Ran’s suggestion in his petichah to Hilkhot Pesach, 1:9).