Verse Text
karkaśaṁ trividhaṁ proktaṁ vajraṁ svarṇaṁ tathā jatu |
citta-traye ’tra bhāvasya jṣeyā vaiśvānaropamā ||263||
Translation
There are three degrees of hardness: like a thunderbolt, gold and lac. Bhāva is like fire in relation to these three types of hard heart.
Purport (Nectar of Devotion)
A hard heart is compared to a lightning bolt, to gold and to lac.