Srimad Bhagavatam — Shashtha Skandha, Shloka 9
Nārāyaṇa-kavaca — The Armor of Lord Nārāyaṇa
न्यसेद्धृदय ओंङ्कारं विकारमनु मूर्धनि । षकारं तु भ्रुवोर्मध्ये णकारं शिखया न्यसेत् ॥ ८ ॥ वेकारं नेत्रयोर्युञ्ज्यान्नकारं सर्वसन्धिषु । मकारमस्त्रमुद्दिश्य मन्त्रमूर्तिर्भवेद् बुध: ॥ ९ ॥ सविसर्गं फडन्तं तत्सर्वदिक्षु विनिर्दिशेत् । ॐ विष्णवे नम इति ॥ १० ॥
nyased dhṛdaya oṁkāraṁ vi-kāram anu mūrdhani ṣa-kāraṁ tu bhruvor madhye ṇa-kāraṁ śikhayā nyaset
诵六音真言“唵 毗湿那韦 那玛哈”时，将“唵”置于心，“毗”置于顶，“沙”置于眉间，“那”置于发髻，“韦”置于两眼之间；再将“那”置于全身诸关节，并观“玛”为武器，于是行者成为真言之形。最后在“玛”上加发声，向东方起遍诸方诵“玛ḥ 阿斯特拉耶 破吒”。
FAQs
In Canto 6, Chapter 8, Śukadeva explains the Narayana-kavaca as a devotional protective shield, applied through mantra and remembrance of Lord Viṣṇu in all directions.
Parīkṣit was hearing the Bhagavatam as the final and complete shelter before death; Śukadeva therefore taught practices that fix the mind on Viṣṇu and invoke divine protection through bhakti.
Even without technical ritual, one can apply the essence by daily chanting “Oṁ viṣṇave namaḥ,” remembering Viṣṇu’s protection, and beginning work or travel with prayerful mindfulness.