Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 19

Sanskrit:

निवारितो नारदेन तत्सुतौ मृत्युमात्मन: ।ज्ञात्वा लोहमयै: पाशैर्बबन्ध सह भार्यया ॥ १९ ॥

ITRANS:

nivārito nāradenatat-sutau mṛtyum ātmanaḥjñātvā loha-mayaiḥ pāśairbabandha saha bhāryayā

Translation:

But Nārada restrained Kaṁsa by reminding him that it was the two sons of Vasudeva who would cause his death. Kaṁsa then had Vasudeva and his wife shackled in iron chains.

Purport:

Kaṁsa realized that there was no use in killing Vasudeva, since it was Vasudeva’s sons, Kṛṣṇa and Balarāma, who were to kill him. According to the ācāryas, Nārada also advised Kaṁsa that if he killed Vasudeva the two young boys might flee and that it was therefore better not to kill him. Rather, Nārada recommended, Kaṁsa should bring Kṛṣṇa and Balarāma to Kaṁsa’s capital city, Mathurā. Śrīla Viśvanātha Cakravartī points out that Nārada did not act inimically toward the great devotees Vasudeva and Devakī when he revealed this information to Kaṁsa. In fact, as explained in the Eleventh Canto, Vasudeva was grateful to Nārada because he was arranging for Kaṁsa’s death at Kṛṣṇa’s hands, and further arranging for Kṛṣṇa to come and live in Mathurā, where His loving father could associate with Him.