How was it possible for Śiśupāla and Dantavakra, in the presence of many exalted persons, to enter very easily into the body of Kṛṣṇa, whose nature is difficult to attain?
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
एतद्भ्राम्यति मे बुद्धिर्दीपार्चिरिव वायुना । ब्रूह्येतदद्भुततमं भगवांस्तत्र कारणम्
etadbhrāmyati me buddhirdīpārciriva vāyunā | brūhyetadadbhutatamaṃ bhagavāṃstatra kāraṇam
SB 7.1.20