शुक्लः शिवो रक्तशक्त्यां पराशाम्भववेधतः
रक्तशाम्भवरूपेण परातत्त्वेन शक्तितः |
रक्तः शिवः शुक्लशक्त्यां परशक्त्यैक्यभवतः
रक्तः शिवः शुक्लशक्त्यां सच्चिदानन्दलक्षणः ||
śuklaḥ śivo raktaśaktyāṃ parāśāmbhavavedhataḥ
raktaśāmbhavarūpeṇa parātattvena śaktitaḥ |
raktaḥ śivaḥ śuklaśaktyāṃ paraśaktyaikyabhavataḥ
raktaḥ śivaḥ śuklaśaktyāṃ saccidānandalakṣaṇaḥ ||
It is only due to the coming together of śiva and śakti that the state of Pūrnabrahma is attained. At the onset of this process, śiva enters the śakti, but his śivabhāva remains unchanged, unmoving and unperturbed. This act of śiva entering the śakti is of two kinds: as a consort (patibhāva) and as a son (putrabhāva).
Once śiva enters śakti, he attains the form of śakti, or in other words, he verily becomes the śakti. Similarly, śakti verily becomes the śiva.
Now, in the second stage, śaktirūpī-śiva and śivarūpiṇī-śakti come together again (or their conjugation expands and deepens) in an ecstatic embrace, and the result in the complete unfoldment of the light and bliss of Pūrṇabrahma. This is the esoteric sequence of śakti sādhanā.
This pregnant verse requires a commentary that can run into several volumes. The first approach would be to address the philosophical aspect and delineate the concepts of Pariṇāma, ābhāsa, and Svātantrya.
Then there is the angle of Kuṇḍalinī Yoga filled with the secrets of Kulāmnāya which can only be learned from a competent Guru.
The third and the most crucial interpretation is geared towards the practical path of Mantra śāstra. Coded in this verse are the potent mantras – praṇava, māyā, prāsāda, parā, prāsādaparā, parāprāsāda, mahāśāmbhavī, mahāśambhu, parāśāmbhavī, prāsādaśambhu, parāśambhu, prāsādaśaivī, parāprāsādaśaivī, prāsādaparāśaivī, parāprāsādaśāmbhavī, prāsādaparāśāmbhavī, sthūla-kāmakalā, sūkṣma-kāmakalā etc, which constitute the ūrdhvāmnāya guru-pādukā.