Ben Bag Bag said: Turn it over, and [again] turn it over, for all is therein. And look into it; And become gray and old therein; And do not move away from it, for you have no better portion than it.
Ben Hei Hei said: According to the labor is the reward.
In this mishnah, which according to some versions is the final mishnah of the tractate known as Pirkei Avot, the names Ben Bag Bag and Ben Hei Hei, which do not appear elsewhere in the Mishnah, stand out. Some explain that the two were non-Jews who converted to Judaism in a period when the government forbade it, so they were given pseudonyms in order to conceal their identities. According to this explanation, both pseudonyms allude to the letter hei, the letter that was added to the names of Abraham and Sarah [the first Jews after whom all converts are named]: The numerical value of Bag (בַּג) is 5, the same value as the letter hei. Bag Bag (בַּג בַּג) is therefore numerically equivalent to hei hei (ה ה) and of course Ben Hei Hei is itself the letter hei.
Among many things, the letter hei alludes to the structure of the tractate of Avot, both in its original format (which included only 5 chapters) and in the revised format (which includes 6 chapters). Bag (בַּג), which equals 5, alludes to the tractate’s original 5 chapters, which are internally divided into 2 (ב) chapters and 3 (ג) chapters. The first two chapters describe the transfer of the Oral Torah through the generations, while the last three chapters are an anthology of sayings from the sages known as tana’im.
When the letter hei’s name is written out (הא) as in Ben Hei Hei’s name (הֵא הֵא), it alludes to the revised structure of the tractate after another chapter, the sixth chapter was added (particularly in liturgical use). The structure then became: 5 (ה) chapters and 1 (א) additional chapter. The repeating names, Bag Bag and Hei Hei allude to the fact that it is not enough to learn one time, rather constant reviews of what one has learnt are required, as Ben Bag Bag instructed, “Turn it over, and [again] turn it over, for all is therein. Delve and delve into it, for all is in it.”
“Turn it over, and [again] turn it over” also alludes to the teaching of the Zohar that true tzaddikim (pious individuals) must know how to transform the false reality of the world on two accounts. First, they must know how to transform the darkness into light, and second, they must know how to transform bitterness into sweetness.
Transforming darkness into light means elevating the husk of impurity wrapped around reality and called nogah. Nogah serves as an intermediary and transitional stage from the reality of holiness to the three lower husks of impurity—i.e., reality that is entirely separated from God. The husk of nogah is the “seam” between holiness and impurity. As such, it can deteriorate and fall into the completely impure husks. However, it can also ascend to become part of holiness with relative ease. God’s commandments are holy. Transgressions are what make up the impurity. The intermediate realm of nogah refers to all actions that are not commanded but are permissible.
Transforming darkness into light thus translates into taking all our daily permissible acts and elevating them to holiness: for instance, by eating in order to have strength to learn Torah, sleeping in order to regain our energy to serve God, studying a profession in order to provide a good income with which to serve God or to use the knowledge itself to serve God or His Torah.
Transforming bitterness into sweetness is a more difficult task, because it entails transformation of the three impure husks and attaching them to holiness. With the power of our holy Torah, it is possible to elevate even the most inexorable husks into holiness. And who knows that better than Ben Bag Bag, who was a non-Jew who converted and attached himself to the holiness of Israel?
 In the siddur of the Alter Rebbe, this is the next to last Mishnah, followed by “Five years old to learn Torah.”
 Ben Bag Bag appears in the Talmud, sometimes as Yochanan Ben Bag Bag, as in Kidushin 10b.
 Midrash Shmuel in the name of the Rashbam, brought in Tosafot Yom Tov.
 Beginning with “Moshe received Torah from Sinai…to the Men of the Great Assembly,” through the pairs, until Hillel and Shamai. After that, the lineage of all the princes from Hillel and back to Hillel (2:7). After that, “Rabban Yochanan Ben Zakai received from Hillel and Shamai” with the students of Rabbi Yochanan Ben Zakai, until Rabbi Tarfon, who was also a student of Rabbi Yochanan Ben Zakai. (See Rabbi Matityah Hayitzhari and Merkevet Hamishnahi, end of c. 2).
. The sixth chapter is sometimes referred to by the name, “Acquisition of Torah” (קִנְיַן תּוֹרָה) as it mostly deals with the character traits and labor required to acquire knowledge and understanding of Torah.
 See the story brought in Pesachim 50a about Rav Yosef Ben Rib”al.
 As in the words of Rabbi Shimon to the angels (Preface to the Zohar I:4a)
 For more on the husk of nogah, see Eitz Chayim 49:4 and Tanya c. 7.
 See Tanya c. 8.