Class 28, Perek 2, Class 8 Tanya (text based)

One becoming many: It starts with the One Soul of אדם הראשון, which then becomes 7, then 600,000, then each of those (general Souls) has 600,000 sparks. But even after they descend and change they’re still essentially the same: one with their source until חכמה עילאה.