Dīkṣā, Mantra-Types, Mantra-Doṣas, and Qualifications of Ācārya–Śiṣya
अष्टाविंशतिवर्णो वा तथैकत्रिंशदर्णकः । अतिक्रूरः स विज्ञेयोऽखिलकर्मसु गर्हितः ॥ ५१ ॥
aṣṭāviṃśativarṇo vā tathaikatriṃśadarṇakaḥ | atikrūraḥ sa vijñeyo'khilakarmasu garhitaḥ || 51 ||
(真言・唱句が)二十八音節であれ、また三十一音節であれ、きわめて凶猛であると知るべきであり、あらゆる儀礼と行為において用いることは非難される。
Sanatkumara (teaching Narada in a technical/Vedanga context)
Vrata: none
Primary Rasa: shanta
Secondary Rasa: raudra
It emphasizes discernment in sacred speech: certain syllabic structures are considered inherently harsh and therefore unfit for dharmic practice, reminding practitioners that mantra is not merely words but regulated, ethically aligned sound.
Bhakti relies on pure, auspicious utterance (japa, stotra, nāma). The verse indirectly safeguards devotion by warning against using fierce or censured formulas in place of sattvic praise and remembrance of the Divine.
It reflects Śikṣā (Vedic phonetics) and mantra-vicāra: syllable-count and phonetic composition are treated as practical criteria for deciding whether a mantra is ritually appropriate or prohibited.