उमामहेश्वरव्रतं—पञ्चाक्षरमन्त्रस्य माहात्म्यं, न्यासः, जपविधिः, सदाचारः, विनियोगः
गले मध्ये तथाङ्गुष्ठे तर्जन्याद्याङ्गुलीषु च अङ्गुष्ठेन करन्यासं कुर्यादेव विचक्षणः
gale madhye tathāṅguṣṭhe tarjanyādyāṅgulīṣu ca aṅguṣṭhena karanyāsaṃ kuryādeva vicakṣaṇaḥ
明辨之行者当行“手安置”(kara-nyāsa):以触按安置真言于喉中部、于拇指、并于自食指起的诸指之上,皆以拇指作仪轨之触。
Suta Goswami (narrating Shiva-puja-vidhi to the sages of Naimisharanya)
It teaches kara-nyāsa as a required internalizing step of Shiva-mantra before Linga-puja, sanctifying the worshipper’s body as a fit vessel for invoking Pati (Shiva) and loosening pasha (bondage) for the pashu (soul).
By prescribing mantra-imposition on the throat and fingers, it implies Shiva-tattva is approached through mantra embodied in the practitioner—Shiva as Pati is invoked not only externally in the Linga but also established within the worshipper’s own faculties of speech and action.
Kara-nyāsa (mantra placement on thumb and fingers) along with throat placement—an angic practice used in Shaiva puja and Pashupata-oriented sadhana to stabilize mantra, purify action-organs, and prepare for Linga-archana.