Why was King Hezekiah allowed to hide the Book of Healing, thereby causing otherwise preventable deaths?
Berachot 10b.5-7 teaches:1
מַאי ״וְהַטּוֹב בְּעֵינֶיךָ עָשִׂיתִי״? ... רַבִּי לֵוִי אָמַר: שֶׁגָּנַז סֵפֶר רְפוּאוֹת. תָּנוּ רַבָּנַן: שִׁשָּׁה דְבָרִים עָשָׂה חִזְקִיָּהוּ הַמֶּלֶךְ, עַל שְׁלֹשָׁה הוֹדוּ לוֹ, וְעַל שְׁלֹשָׁה לֹא הוֹדוּ לוֹ. עַל שְׁלֹשָׁה הוֹדוּ לוֹ: גָּנַז סֵפֶר רְפוּאוֹת — וְהוֹדוּ לוֹ. ...
What is "The good in your eyes I have done?" ... R' Levi said, "That he hid the Book of Healing." The Rabbis taught [in a Braisa]: King Hezekiah did six things; regarding three of them [the Rabbis] agreed to him, and regarding three of them they did not agree to him. Regarding three of them they agreed to him: He hid the Book of Healing, and they agreed to him; ...
In explaining what the Book of Healing was, Ben Yehoyada to the parallel in Pesachim 56a.2 explains:1
נראה לי הספר הזה היה בו חכמה נפלאה של עשבים שאין שום חולי בעולם שאין לו רפואה גמורה על ידי מין עשב אחד ובכלל זה יש בו סגולות עשבים שיש עשב חותך ברזל ויש מושך דבר שאי אפשר למשכו בידים מרוב קוטנו ויש עושה אהבה ויש עושה שנאה בין אדם לחברו ובין איש לאשתו ועוד ועוד כמה דברים עד אין מספר.
It appears to me that this book contained wondrous wisdom regarding herbs, for no ailment in the world cannot be completely cured by way of an herbal remedy. Included in this are some treasured herbs: there is an herb which can cut iron; there is an herb which allows one to pull something immovable by hand because of its small size; there one which creates love, and one which creates hatred, between man and his friend, or between man and his wife; and many others to no end.2
Rashi explains Hezekiah's intentions in destroying such an important book on the parallel in Pesachim:1
לפי שלא היה לבם נכנע על חולים אלא מתרפאין מיד
Because their hearts were not humbled by their ailments; rather, they were healed immediately.
However noble his intentions, Hezekiah sentenced people to death in doing so. Taking these sources literally, Hezekiah destroyed the cure to cancer!
The law is that saving a life takes precedence over nearly everything (Sanhedrin 74a). Hezekiah wasn't faced with choosing between saving a life and killing someone, worshipping idols, or illicit relations, nor would even a lesser prohibition be violated in public had he kept the book.3 So why was Hezekiah allowed to forfeit all the millions of lives lost with his destruction of this knowledge?
All translations are my own. ↩
By his referencing plants which can cut iron or lift small objects, I infer that he does not necessarily mean that every plant has a unique remedy; rather, some plants are especially skilled for some tasks. Not every plant can be turned into a thin wire for a metal saw, or a set of tweezers, but there are certainly multiple types of plants which do. With this interpretation, this piece of Ben Yehoyada is entirely in agreement with modern science. ↩
This is the critical point of the question, of course, and it's entirely based on Rashi's understanding which I cited. This is not the only approach to this story; Rambam, for instance, on his commentary to Pesachim 4:9, explains that the cures discussed in the book were ones forbidden to practice. With that in mind, please try to answer this question specifically according to Rashi, or perhaps according to a different commentator who does not appeal to preventing sin as Hezekiah's motivation, but not to commentaries such as Rambam. ↩