SB 2.7.30

gṛhṇīta yad yad upabandham amuṣya mātā
 śulbaṁ sutasya na tu tat tad amuṣya māti
yaj jṛmbhato ’sya vadane bhuvanāni gopī
 saṁvīkṣya śaṅkita-manāḥ pratibodhitāsīt
Word for word: 
gṛhṇīta — by taking up; yat yat — whatsoever; upabandham — ropes for tying; amuṣya — His; mātā — mother; śulbam — ropes; sutasya — of her son; na — not; tu — however; tat tat — by and by; amuṣya — His; māti — was sufficient; yat — that which; jṛmbhataḥ — opening the mouth; asya — of Him; vadane — in the mouth; bhuvanāni — the worlds; gopī — the cowherd woman; saṁvīkṣya — so seeing it; śaṅkita-manāḥ — doubtful in mind; pratibodhitā — convinced in a different way; āsīt — was so done.
Translation: 
When the cowherd woman [Kṛṣṇa’s foster mother, Yaśodā] was trying to tie the hands of her son with ropes, she found the rope to be always insufficient in length, and when she finally gave up, Lord Kṛṣṇa, by and by, opened His mouth, wherein the mother found all the universes situated. Seeing this, she was doubtful in her mind, but she was convinced in a different manner of the mystic nature of her son.
Purport: 

One day Lord Kṛṣṇa as the naughty child disturbed His mother Yaśodā, and she began to tie up the child with ropes just to punish Him. But no matter how much rope she used, she found it always insufficient. Thus she became fatigued, but in the meantime the Lord opened His mouth, and the affectionate mother saw within the mouth of her son all the universes situated together. The mother was astonished, but out of her deep affection for Kṛṣṇa she thought that the Almighty Godhead Nārāyaṇa had kindly looked after her son just to protect Him from all the continuous calamities happening to Him. Because of her deep affection for Kṛṣṇa, she could never think that her very son was Nārāyaṇa, the Personality of Godhead Himself. That is the action of yoga-māyā, the internal potency of the Supreme Lord, which acts to perfect all the pastimes of the Lord with His different types of devotees. Who could play such wonders without being God?