Srimad Bhagavatam Canto 03, Chapter 14, Text 32

SB 3.14.32

athopasprsya salilam
 pranan ayamya vag-yatah
dhyayañ jajapa virajam
 brahma jyotih sanatanam
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Thereafter the brahmana took his bath in the water and controlled his speech by practicing trance, meditating on the eternal effulgence and chanting the holy Gayatri hymns within his mouth.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
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. Kasyapa Muni meditated on the impersonal brahmajyoti by chanting the Gayatri 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 kirtana. The Vedic hymn Hare Krsna, Hare Krsna, Krsna Krsna, Hare Hare/ Hare Rama, Hare Rama, Rama Rama, Hare Hare can be chanted both softly to oneself or loudly; therefore it is called the maha-mantra, or the great hymn.
 
Kasyapa Muni appears to be an impersonalist. Comparing his character with that of Thakura Haridasa as referred to above, it is clear that the personalist is stronger in sense control than the impersonalist. This is explained in Bhagavad-gita as param drstva 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 Gayatri, but the maha-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.
Srimad Bhagavatam Canto 03, Chapter 14, Text 31
Srimad Bhagavatam Canto 03, Chapter 14, Text 33