As I Heard Them, Vol. 1, pp. 162-163, no. 43 · The Rebbe Rashab
When we were in Lubavitch, ” the Rebbe said, “we could not imagine the darkness of Rostov. For someone whom the darkness doesn’t bother, it brings him no benefit; but one who is disturbed by the darkness — and who overcomes it — reaps its additional light. ”¹⁵
15. Zohar, Section 3, 47b: The superiority of light over darkness — signifying as well, the superiority of light that comes from darkness.