SB 3.14.32

athopaspṛśya salilaṁ
 prāṇān āyamya vāg-yataḥ
dhyāyañ jajāpa virajaṁ
 brahma jyotiḥ sanātanam
Synonyms: 
atha — thereafter; upaspṛśya — touching or taking bath in water; salilam — water; prāṇān āyamya — practicing trance; vāk-yataḥ — controlling speech; dhyāyan — meditating; jajāpa — chanted within the mouth; virajam — pure; brahma — Gāyatrī hymns; jyotiḥ — effulgence; sanātanam — eternal.
Translation: 
Thereafter the brāhmaṇa took his bath in the water and controlled his speech by practicing trance, meditating on the eternal effulgence and chanting the holy Gāyatrī hymns within his mouth.
Purport: 

As one has to take bath after using the toilet, so one has to wash himself with water after sexual intercourse, especially when at a forbidden time. Kaśyapa Muni meditated on the impersonal brahmajyoti by chanting the Gāyatrī mantra within his mouth. When a Vedic mantra is chanted within the mouth so that only the chanter can hear, the chanting is called japa. But when such mantras are chanted loudly, it is called kīrtana. The Vedic hymn Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare can be chanted both softly to oneself or loudly; therefore it is called the mahā-mantra, or the great hymn.

Kaśyapa Muni appears to be an impersonalist. Comparing his character with that of Ṭhākura Haridāsa as referred to above, it is clear that the personalist is stronger in sense control than the impersonalist. This is explained in Bhagavad-gītā as paraṁ dṛṣṭvā nivartate; i.e., one ceases to accept lower-grade things when one is situated in a superior condition. One is supposed to be purified after taking bath and chanting Gāyatrī, but the mahā-mantra is so powerful that one can chant loudly or softly, in any condition, and he is protected from all the evils of material existence.