Narada Purana — Purva Bhaga, Shloka 29
Dīkṣā, Mantra-Types, Mantra-Doṣas, and Qualifications of Ācārya–Śiṣya
न विद्येते स मंत्रस्तु स्तंभितः सिद्धिरोधकृत् । अग्निः पवनसंयुक्तो मनोर्यस्य तु मूर्द्धनि ॥ २९ ॥
na vidyete sa maṃtrastu staṃbhitaḥ siddhirodhakṛt | agniḥ pavanasaṃyukto manoryasya tu mūrddhani || 29 ||
此咒并非真正“存在”（即不发生功用）；它被阻滞，致使悉地（成就）受遮断。若有人头顶之处，火（内热）与风（气息）相合，则其心意为之扰乱，受阻而不畅。
Sanatkumara (teaching Narada in a technical/vedanga-oriented section)
Vrata: none
Primary Rasa: shanta
Secondary Rasa: bhayanaka
FAQs
It warns that mantra practice can become ‘stambhita’—ineffective—when inner forces like heat and breath agitate the mind, thereby obstructing siddhi and spiritual progress.
Even in devotion, steadiness of mind is essential; when the mind is disturbed, japa and remembrance lose their potency, so inner discipline supports sustained bhakti.
It highlights a technical principle relevant to mantra-prayoga: improper management of prāṇa (pavana) and inner heat (agni) can disturb the mind and hinder mantra-siddhi—implying the need for correct method and regulation.