The original source is replied immediately in the next sūtra, next code: janmādy asya yataḥ (SB 1.1.1). The original source, either of happiness or of distress, everything original source is that. Simply giving original . . . janmādy asya yataḥ, wherefrom everything emanates. Distress also emanates and happiness also emanates. This cosmic manifestation also emanates. The supply also emanates. Everything emanates, the supreme source. Now you can explain. Everything emanates.
How is that, distress also emanates and happiness also emanates; knowledge also emanates, ignorance also emanates? Yes. That is fullness. That is fullness. This is the . . . how that original source is for everything, that is explained in the Bhagavad-gītā, Bhāgavata also. Kṛṣṇa says in the Bhagavad-gītā that ahaṁ sarvasya prabhavaḥ (BG 10.8) "I am the source of everything. I am the source of happiness, I am the source of distress, I am the source of all this Brahmā, Viṣṇu, Maheśvara—everything." Mattaḥ parataraṁ nāsti (BG 7.7) "There is no more supreme source than Me."
Then why these two things, duality, distress and happiness? That is also answered in the Bhagavad-gītā. You'll find, sarvasya cāhaṁ hṛdi sanniviṣṭo mattaḥ smṛtir jñānam apohanaṁ ca (BG 15.15) "I am sitting in everyone's heart, and from Me there is memorization and forgetfulness."