O King Parīkṣit, within a very short time both Rāma and Kṛṣṇa began to walk very easily in Gokula on Their legs, by Their own strength, without the need to crawl.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
कालेनाल्पेन राजर्षे रामः कृष्णश्च गोकुले । अघृष्टजानुभिः पद्भिर्विचक्रमतुरञ्जसा
kālenālpena rājarṣe rāmaḥ kṛṣṇaśca gokule | aghṛṣṭajānubhiḥ padbhirvicakramaturañjasā
SB 10.8.26