Kansa informed by Nārada of the existence of Krishna and Balarāma; he sends Kesin to destroy them and Akrura to bring them to Mathura - Verse 6
Vishnu Purana (GRETIL; M. M. Pathak critical edition) · 4 · Verse 15.6
Sanskrit Original
नातस तस्मिन्न अनादिनिधने परब्रह्मभूते भगवत्य अनालम्बनीकृते मनसस तल्लयम। दशाननत्वे ऽप्य अनङ्गपराधीनतया जानकीसक्तचेतसो दाशरथिरूपधारिणस तद्रूपदर्शनम एवासिन नायम अच्युत इत्य आसक्तिर विपद्यतो ऽन्तःकरणस्य मानुषबुद्धिर एव केवलम अस्याभूत।।
nātas tasminn anādinidhane parabrahmabhūte bhagavaty anālambanīkṛte manasas tallayam| daśānanatve 'py anaṅgaparādhīnatayā jānakīsaktacetaso dāśarathirūpadhāriṇas tadrūpadarśanam evāsin nāyam acyuta ity āsaktir vipadyato 'ntaḥkaraṇasya mānuṣabuddhir eva kevalam asyābhūt||
In that state, there is no dependence on the eternal, supreme Brahman, the divine, which is beyond the mind's grasp. Even in the form of the ten-headed one, being under the influence of love for Janaki, Dasaratha manifests that form. Thus, the attachment to the imperishable is solely the human intellect's creation.