Canto 2 -
Ayodhyā-kāṇḍa
Chapter 21: Rāma Consoles Kausalyā and Lakṣmaṇa
Text 2.21.29

ततस्त्वं प्राप्स्यसे पुत्र निरयं लोकविश्रुतम्।
ब्रह्महत्यामिवाधर्मात्समुद्रः सरितां पतिः॥

tatas tvaṁ prāpsyase putra nirayaṁ loka-viśrutam
brahma-hatyām ivādharmāt samudraḥ saritāṁ patiḥ

tataḥ = then; tvam = You; prāpsyase = will attain; putra = son; nirayam = hellish distress; loka-viśrutam = famous all over the world; brahma-hatyām = [attained] the special hells reserved for killing a brāhmaṇa; iva = just as; adharmāt = because he engaged in adharma by displeasing his mother; samudraḥ = Samudra; saritām = of the demigoddesses presiding over the rivers; patiḥ = the husband.

Son, You will then attain hellish distress famous all over the world just as Samudra, the husband of the demigoddesses presiding over the rivers, [attained] the special hells reserved for killing a brāhmaṇa because he engaged in adharma by displeasing his mother.1

As alluded to in text 25, a son of Kaśyapa had served his mother and attained the celestial world as a result. He then became a Prajāpati too. This is described in the Purāṇic literature which also describe [the incident concerning] Samudra [mentioned here].

GLOSS. Madhvācārya’s comment on the Fourth Canto of Śrīmad-Bhāgavatam notes:

karmaṇā manasā vācā sarvāvasthāsu sarvadā
akleśa-jananaṁ proktam ahiṁsā tv iha yogibhiḥ

“Yogīs declare ahiṁsā or nonviolence to be the nongeneration of distress in thought, word or deed under all circumstances and at all times.”1 

1 Samudra refers to the presiding demigod of the ocean.

1 From this perspective, Samudra had engaged in hiṁsā or violence to his mother. Therefore he accrued the sinful reaction of killing a brāhmaṇa.