Reference for Bava Batra 6:4
הַמּוֹכֵר מָקוֹם לַחֲבֵרוֹ לִבְנוֹת לוֹ בַיִת, וְכֵן הַמְקַבֵּל מֵחֲבֵרוֹ לִבְנוֹת לוֹ בֵית חַתְנוּת לִבְנוֹ וּבֵית אַלְמְנוּת לְבִתּוֹ, בּוֹנֶה אַרְבַּע אַמּוֹת עַל שֵׁשׁ, דִּבְרֵי רַבִּי עֲקִיבָא. רַבִּי יִשְׁמָעֵאל אוֹמֵר, רֶפֶת בָּקָר הוּא זֶה. הָרוֹצֶה לַעֲשׂוֹת רֶפֶת בָּקָר, בּוֹנֶה אַרְבַּע אַמּוֹת עַל שֵׁשׁ. בַּיִת קָטָן, שֵׁשׁ עַל שְׁמֹנֶה. גָדוֹל, שְׁמֹנֶה עַל עֶשֶׂר. טְרַקְלִין, עֶשֶׂר עַל עֶשֶׂר. רוּמוֹ כַּחֲצִי אָרְכּוֹ וְכַחֲצִי רָחְבּוֹ. רְאָיָה לַדָּבָר, הֵיכָל. רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל אוֹמֵר, הַכֹּל כְּבִנְיַן הֵיכָל:
If one sells a place to his neighbor to build a house for him; likewise, one who is commissioned by his neighbor to build a "wedding house" for his son, [it being customary to build a house for one's son when he marries], or a "widowhood house" for his daughter, [when her husband dies and she returns to her father's house. But in her husband's lifetime she is with her husband, it not being customary for a man to live with his in-laws], he builds (at least) four by six cubits. These are the words of R. Akiva. R. Yishmael says: This is a cattle shed! [i.e., He must build it larger.] If one wishes to make a cattle shed, he builds four cubits by six. A small house is six by eight. [The smallest of houses is six by eight, and if one sells a place to his neighbor to build a house for him, the house must be (at least) six by eight.] [If he specified] "a large house," (it must be (at least) eight by ten. A "house of state," ten by ten. Its height must be (the sum of) half its length and half its width. [This refers to all of the above, viz.: For a small house, the height is seven cubits; for a large house, nine; and for a "house of state," ten.] Confirmation of this — the (Temple) sanctuary, (which was forty in length, twenty in width, and thirty in height — half the sum of the length and the width.) R. Shimon b. Gamliel says: All according to the structure of the sanctuary. [Some understand this to mean: It is R. Shimon b. Gamliel who taught: "Its height must be … Confirmation of this, etc." Others understand it as R. Shimon b. Gamliel differing with the first tanna, expressing wonder, viz.: "Is everything to be built according to the structure of the sanctuary!" The criterion, rather, is "the custom of the land."]