Tractate Yadayim - Chapter 3 - Mishnah 5 ידיים פרק ג׳ משנה ה׳

A scroll on which the writing has become erased and eighty-five letters remain, as many as are in the section beginning, "And it came to pass when the ark set forward" (Numbers 10:35-36) defiles the hands. A single sheet on which there are written eighty-five letters, as many as are in the section beginning, "And it came to pass when the ark set forward", defiles the hands. All the Holy Scriptures defile the hands. The Song of Songs and Kohelet (Ecclesiastes) defile the hands. Rabbi Judah says: the Song of Songs defiles the hands, but there is a dispute about Kohelet. Rabbi Yose says: Kohelet does not defile the hands, but there is a dispute about the Song of Songs. Rabbi Shimon says: [the ruling about] Kohelet is one of the leniencies of Bet Shammai and one of the stringencies of Bet Hillel. Rabbi Shimon ben Azzai said: I have received a tradition from the seventy-two elders on the day when they appointed Rabbi Elazar ben Azariah head of the academy that the Song of Songs and Kohelet defile the hands. Rabbi Akiba said: Far be it! No man in Israel disputed that the Song of Songs [saying] that it does not defile the hands. For the whole world is not as worthy as the day on which the Song of Songs was given to Israel; for all the writings are holy but the Song of Songs is the holy of holies. If they had a dispute, they had a dispute only about Kohelet. Rabbi Yohanan ben Joshua the son of the father-in-law of Rabbi Akiva said in accordance with the words of Ben Azzai: so they disputed and so they reached a decision.