Midrash sur La Genèse 17:7

Our Rabbis were taught (Num. 10, 36) And when it rested, he said, 'Return O Lord to the myriads and thousands of Israel.' (Fol. 64) Infer from this that the Shechina does not rest upon less than two myriads and two thousands Israelites. Suppose Israel numbered twenty-two thousand less one, and there be one amongst them who did not marry, is he not the cause which prevents the Shechina from resting upon Israel? [Hence the sin of being unmarried is great]. Abba Chanin said in the name of R. Elazar: "Such a man is subject to a penalty of death, as it is said (Ib. 3, 4) And they had no children, — this allows the inference that if they had had children they would not have died." Others again say that such a person causes [directly] the Shcehina to depart from Israel, as it is said (Gen. 17, 7) To be a God unto thee, and to thy seed after thee; i.e., as long as there are seed after thee, the Shechina will rest; but if there are no seed after thee, then upon whom else shall it rest, upon the woods or the mountains?

An idolater asked Rabban Gamliel, "Why was the Holy One, Blessed be He revealed to Moses in the Burning Bush?" Rabban Gamliel replied to him, "If God had been revealed in a carob tree or a fig tree, you would have asked me the same thing, and I could not send you away without an answer. This teaches you that there is no place in the world devoid of the Shekhinah."