Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · War Astrology: Yogas, Nakshatras
युद्धजयार्णवः (योगाः नक्षत्राणि)
काष्ठमध्ये यथा वह्निरप्रवृद्धो न दृश्यते ।विद्यमाना तथा देहे शिवशक्तिर्न दृश्यते ॥ ७ ॥
In the full Agni Purana this is chapter 124, verse 7.
Fire is not seen in the middle of wood when it has not grown. In the same way, Shiva and Shakti, present in the body, are not seen.
Simple meaning: As fire is hidden in wood, Shiva and Shakti are hidden in the body.
आदौ शक्तिः समुत्पन्ना ओंकारस्वरभूषिता ।
First Shakti arose with Om. Then the dot stood in place with the vowel e.
जातो नाद उकारस्तु नदते हृदि संस्थितः ।
The sound u sits in the heart. The half-moon i shows the path to liberation.
अकारोऽव्यक्त उत्पन्नो भोगमोक्षप्रदः परः ।
The letter a is unseen and beyond, and gives enjoyment and liberation. It holds earth and the part called Nivritti.