Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · War Astrology: Yogas, Nakshatras
युद्धजयार्णवः (योगाः नक्षत्राणि)
ऋग्यजुःसामाथर्वाख्यवेदमन्त्राः क्रमेण ते ।सद्योजातादयो मन्त्रा ब्रह्मा विष्णुश्च रुद्रकः ॥ ५ ॥
In the full Agni Purana this is chapter 124, verse 5.
They are, in order, the mantras of the Vedas called Rig, Yajur, Sama and Atharva. Sadyojata and the rest are mantras. They are Brahma, Vishnu and Rudra.
Simple meaning: The five mantras match the four Vedas and Sadyojata and the others, with Brahma, Vishnu and Rudra.
ईशः सप्तशिखा देवाः शब्दाद्याः पञ्च च स्वराः ।
Ishana, the seven-flamed gods, the five sense qualities and the five vowels are named. The root is Brahma.
काष्ठमध्ये यथा वह्निरप्रवृद्धो न दृश्यते ।
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.