From Sefer Teshuot Chen, Parshat Tazria, by Gedaliyahu of Linits (a disciple of Yaakov Yosef of Polnoye and one of the primary sources for tales about the Baal Shem Tov): The Baal Shem Tov taught that when the Messiah comes he will expound on all the words of the Torah, from start to finish, by every possible letter combination in every word, and then he will make from all of the Torah a single word, and from this single word will arise infinite combinations and he will expound on every one of them. (1)
From Kitvei Kodesh 26a (2): It is taught that all of the world stands on the ten utterances of Creation, “and G!d said, Let there be…”. But there are only nine utterances! The Baal Shem Tov taught that the first utterance was too clear and too splendid to be perceived.
From Tshuot Chen Parshat Chayei Sarah and Likutim Leparshat Shlach: This is how the Baal Shem Tov explained the concept of tzimtzum, or divine withdrawal (3), spoken of by the Kabbalists: it all began with G!d wanting to do good to Creation [that is, something other than G!d’s self]. When the Holy One of Blessing saw the acts of the righteous, G!d deeply longed to do good to them, and so the thought arose to create the world, but G!d’s lovingkindness was so overpowering that it overwhelmed everything, leaving no room for anything but G!d. So G!d looked upon the acts of the wicked, and this awoke the divine rigor which caused G!d’s infinite light to withdraw [leaving room for something besides G!d], and in this way the world could be created.
From Chesed L’Avraham, Bereishit 2:2: The Baal Shem Tov taught that all the worlds are “garments” and “thrones” one for the other, all the way down to the lowest worlds, and so even the letters of the alef-bet are “thrones” for one another. (4)
From Degel Mahane Efraim, Parshat Re’eh: I heard from my master, my [grand]father, my teacher [the Baal Shem Tov] an explanation of the verse, ‘And David blessed G!d before the eyes of all the assembly…’, that David made them literally see that ‘all the world is filled with G!d’s glory,’ and ‘there is no place G!d is not.’ How did he show them? With [the rest of the verse], “Yours is the greatness and the might and the glory, and the splendor and the majesty, for all in the heavens and on the earth is Yours, and Yours is the Sovereignty,” [and these things represent the seven lower sefirot]. Then all the nations too saw that the Holy One of Blessing is the source of every thing and every event. (5)
From Keter Shem Tov II, 2a: In every motion the Holy One of Blessing is found, for it is impossible to make a single motion or speak a single word without the power of the Creator, and this is the meaning of the verse, ‘All the world is filled with G!d’s glory.’
From Likutim Yekarim 17:3 (6): ‘All the world is filled with G!d’s glory’ — glory, kavod, also means “clothing,” for G!d is clothed in the world, even the material world.
From Keter Shem Tov II, Ramzei Parshat Bereishit: ‘And Elohim said, Let there be light, and there was light.’ That is, G!d “said” [if we can say such a thing] with the power of the divine attribute “Elohim,” which is divine rigor and the contraction of G!d’s infinite light, and thus “there was light,” that is, the light took on a form that the world could withstand.
From Chinuch Beit Yehuda, by Yaakov Tzvi Eliyash (1869): Our sages taught that G!d hid away the primordial light of creation (7). Where did G!d hide such a light, that filled the whole world, and by which one could see from one end of the world to the other? The Baal Shem Tov taught that G!d hid it in the Torah, for the sages say that Torah is thousands of times greater even than the world (8), and whoever studies Torah for its own sake merits this hidden light.
1) The Zohar on Parshat Shmini says “All of the Torah is one holy name for the Holy One of Blessing.” 2) A collection of Hasidic teachings attributed to the Baal Shem Tov, Dov Ber of Mezeritch, and others, published in 1862. 3) Tzimtzum means (most) literally “withdrawal,” and the idea (from the Arizal) is that, since G!d is infinite and G!d’s presence is too overpowering to allow for anything that is not G!d, the first act of creation was actually G!d’s withdrawing from a certain space within the infinite light, to “make room” for Creation. Usually, when the Hasidim use this term, they use it in the sense of “contraction,” as in G!d contracts the divine self into the essence of creation, that is, the divine spark in each created thing. 4) “Garments” and “thrones” are metaphors for manifestations, usually of a higher plane of existence by a lower plane of existence; what’s striking here is the idea that there is not a hierarchy, rather, everything is a manifestation of everything else, just as every letter holds within it every other letter, that is, every thing is everything. This complements the teaching that each sefirah actually contains within it every other sefirah. 5) I Chronicles 29:10, Isaiah 6:3, Tikkunei Zohar 57; the italicized words are each names for the seven lower sefirot, and this verse is the Biblical “proof text” for them. 6) One of the earliest collections of Hasidic teachings, attributed to the Baal Shem Tov, Dov Ber of Mezeritch, and others, published in 1782. 7) Bereishit Rabbah 3 and 11 8) Eruvin 21a