The verse in Michah (7:8) says:
כִּ֥י נָפַ֖לְתִּי קָ֑מְתִּי כִּֽי־אֵשֵׁ֣ב בַּחֹ֔שֶׁךְ יְהוָ֖ה א֥וֹר לִֽי
As I have fallen, I have risen; as I sit in the darkness, Hashem is a Light to me.
The Orchos Tzaddikim (26:132) quotes "Rabboseinu Zichronam Livracha," without saying where, as saying the following on this verse:
אלמלא שנפלתי לא קמתי אלמלא שישבתי בחושך לא היה אור לי
Had I not fallen, I could not have risen; had I not sat in the darkness, He could not have been a Light for me.
No matter how hard I searched, I could not find a source for this statement. Well, that's not exactly true. I saw it cited in Shir HaShirim Rabbah 6 and Midrash Shocher Tov 22, but, as I learned here, it's a good idea to double-check what source you're sent to. And, in fact, although both sources quote the verse (numerous times, actually), neither actually contains this particular derashah on it. Midrash Tehillim 22:7 contains the same idea, but not those words.
And so, I ask if anyone here has seen this exposition before and, if so, could you please direct me to where it actually is?