Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 37
Sanskrit:
द्विजस्तयोस्तं महिमानमद्भुतंसंलक्ष्य राजन्नतिमानुषीं मतिम् ।सम्मन्त्र्य पत्न्या स महार्णवे मृतंबालं प्रभासे वरयां बभूव ह ॥ ३७ ॥
ITRANS:
dvijas tayos taṁ mahimānam adbhutaṁsaṁlokṣya rājann ati-mānusīṁ matimsammantrya patnyā sa mahārṇave mṛtaṁbālaṁ prabhāse varayāṁ babhūva ha
Translation:
O King, the learned brāhmaṇa Sāndīpani carefully considered the two Lords’ glorious and amazing qualities and Their superhuman intelligence. Then, after consulting with his wife, he chose as his remuneration the return of his young son, who had died in the ocean at Prabhāsa.
Purport:
According to Śrīla Viśvanātha Cakravartī, the child was captured by the conchshell demon while playing at the Mahā-śiva-kṣetra.