SB 10.12.25

itthaṁ mitho ’tathyam ataj-jña-bhāṣitaṁ
 śrutvā vicintyety amṛṣā mṛṣāyate
rakṣo viditvākhila-bhūta-hṛt-sthitaḥ
 svānāṁ niroddhuṁ bhagavān mano dadhe
Synonyms: 
ittham — in this way; mithaḥ — or another; atathyam — a subject matter that is not a fact; a-tat-jña — without knowledge; bhāṣitam — while they were talking; śrutvā — Kṛṣṇa hearing them; vicintya — thinking; iti — thus; amṛṣā — actually, truly; mṛṣāyate — who is trying to appear as a false thing (actually the animal was Aghāsura, but because of poor knowledge they were thinking him to be a dead python); rakṣaḥ — (Kṛṣṇa, however, could understand that) he was a demon; viditvā — knowing it; akhila-bhūta-hṛt-sthitaḥ — because He is antaryāmī, situated everywhere, in the core of everyone’s heart; svānām — of His own associates; niroddhum — just to forbid them; bhagavān — the Supreme Personality of Godhead; manaḥ dadhe — made up His mind.
Translation: 
The Supreme Personality of Godhead, Śrī Kṛṣṇa, who is situated as antaryāmī, the Supersoul, in the core of everyone’s heart, heard the boys talking among themselves about the artificial python. Unknown to them, it was actually Aghāsura, a demon who had appeared as a python. Kṛṣṇa, knowing this, wanted to forbid His associates to enter the demon’s mouth.