Commentary for Bava Batra 6:8
הַמּוֹכֵר מָקוֹם לַחֲבֵרוֹ לַעֲשׂוֹת לוֹ קֶבֶר, וְכֵן הַמְקַבֵּל מֵחֲבֵרוֹ לַעֲשׂוֹת לוֹ קֶבֶר, עוֹשֶׂה תוֹכָהּ שֶׁל מְעָרָה אַרְבַּע אַמּוֹת עַל שֵׁשׁ, וּפוֹתֵחַ לְתוֹכָהּ שְׁמֹנָה כוּכִין, שְׁלֹשָׁה מִכָּאן וּשְׁלֹשָׁה מִכָּאן וּשְׁנַיִם מִכְּנֶגְדָּן, וְכוּכִין אָרְכָּן אַרְבַּע אַמּוֹת וְרוּמָן שִׁבְעָה וְרָחְבָּן שִׁשָּׁה. רַבִּי שִׁמְעוֹן אוֹמֵר, עוֹשֶׂה תוֹכָהּ שֶׁל מְעָרָה שֵׁשׁ אַמּוֹת עַל שְׁמֹנֶה, וּפוֹתֵחַ לְתוֹכָהּ שְׁלֹשָׁה עָשָׂר כּוּךְ, אַרְבָּעָה מִכָּאן וְאַרְבָּעָה מִכָּאן וּשְׁלֹשָׁה מִכְּנֶגְדָּן וְאֶחָד מִימִין הַפֶּתַח וְאֶחָד מִן הַשְּׂמֹאל. וְעוֹשֶׂה חָצֵר עַל פִּי הַמְּעָרָה שֵׁשׁ עַל שֵׁשׁ, כִּמְלֹא הַמִּטָּה וְקוֹבְרֶיהָ, וּפוֹתֵחַ לְתוֹכָהּ שְׁתֵּי מְעָרוֹת, אַחַת מִכָּאן וְאַחַת מִכָּאן. רַבִּי שִׁמְעוֹן אוֹמֵר, אַרְבַּע, לְאַרְבַּע רוּחוֹתֶיהָ. רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל אוֹמֵר, הַכֹּל לְפִי הַסָּלַע:
If one sells a place to his neighbor to make a grave for himself; likewise, if one is commissioned by his neighbor to make a grave for him, he makes the middle of the (burial) cave four cubits [wide] by six [cubits] long, and opens into it eight graves: three on one side and three on the other [on the two sides of the length of the cave], and two opposite [the entrance of the cave], each grave four cubits long, six cubits wide, and seven cubits high [so that between each grave on the sides there are one and a half cubits; and between the two at the end, two cubits.] R. Shimon says: He makes the middle of the grave six cubits by eight, and opens into it thirteen graves: four on one side and four on the other, three opposite (the entrance), one to the right of the entrance and one to the left. And a courtyard is made before the cave, six by six, the fullness of (i.e., large enough to contain) the litter and its buriers; and two caves are opened into it, one on each side. R. Shimon says: Four, on its four sides. R. Shimon b. Gamliel says: All according to the (hardness) of the rock. [If it is hard, he is required to dig only six cubits long and four cubits wide, as per the first tanna; and if it is soft and loose, he is required to dig six by eight as per R. Shimon. The halachah is in accordance with the first tanna.]
Bartenura on Mishnah Bava Batra
English Explanation of Mishnah Bava Batra
Rabbi Shimon says: “He must make the inside of the vault four cubits by eight, and open within it thirteen niches, four on this side, four on that side, three opposite [the doorway] and one to the right of the doorway and one to the left.
He must make a courtyard at the opening of the vault, six cubits by six, space enough for the bier and its bearers. And he may open within it two vaults, one on either side. Rabbi Shimon says: “Four, one on each of its sides.”
Rabban Shimon ben Gamaliel says: “All depends on the nature of the rock.”
Mishnah eight deals with the building of tombs.
In the times of the mishnah people were buried in tombs, which consisted of caves with niches carved out of the wall. Each tomb could hold a number of bodies, with one body put into each niche. If someone contracted to build a tomb he must build one 4 by 6 cubits (2 by 4 meters) and make eight niches, each of a specified length, width and height. According to Rabbi Shimon, the tomb must be 4 by 8 cubits and contain 13 niches. In addition, he must build a courtyard over the tomb, big enough for the bier, a stretcher which carried the body and the people holding the bier. According to the anonymous opinion in 3a, the courtyard can serve two tombs and according to Rabbi Shimon it can serve four.
Rabban Shimon ben Gamaliel, section 4, disagrees with Rabbi Shimon and the anonymous opinion in section 1. According to Rabban Shimon ben Gamaliel the size of the tomb is not set in absolute terms, but depends on the nature of the rock. If it is hard rock he is only obligated to make eight niches in a 4 by 6 tomb, but if it is soft rock, he is obligated to make thirteen niches in a 4 by 8 tomb.