Matsyapurana 146.41

146.41

vajrāsāramayair aṅgair achedyairāyasair dṛḍhaiḥ
vajrāṅgo nāma putraste bhavitā putravatsale //

The sage said to his grieved consort that she would beget such a progeny after practising penances for ten thousand years "You will beget Vajranga whose body will be as massive as thunderbolt and iron, so no weapons would baffle him"—40 41