Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 42

Sanskrit:

तं वत्सरूपिणं वीक्ष्य वत्सयूथगतं हरि: ।दर्शयन् बलदेवाय शनैर्मुग्ध इवासदत् ॥ ४२ ॥

ITRANS:

taṁ vatsa-rūpiṇaṁ vīkṣyavatsa-yūtha-gataṁ hariḥdarśayan baladevāyaśanair mugdha ivāsadat

Translation:

When the Supreme Personality of Godhead saw that the demon had assumed the form of a calf and entered among the groups of other calves, He pointed out to Baladeva, “Here is another demon.” Then He very slowly approached the demon, as if He did not understand the demon’s intentions.

Purport:

The import of the words mugdha iva is that although Kṛṣṇa knows everything, here He pretended that He did not understand why the demon had entered among the calves, and He informed Baladeva by a sign.