tokena jiva-haranam yad uluki-kayas
trai-masikasya ca pada sakato ’pavrttah
yad ringatantara-gatena divi-sprsor va
unmulanam tv itaratharjunayor na bhavyam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
There is no doubt about Lord Krsna’s being the Supreme Lord. Otherwise, how was it possible for Him to kill a giant demon like Putana when He was just on the lap of His mother, to overturn a cart with His leg when He was only three months old, or to uproot a pair of arjuna trees so high that they touched the sky, when He was only crawling? All these activities are impossible for anyone other than the Lord Himself.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
One cannot manufacture a God by one’s mental speculation or by numerical votes, as has become a practice for the less intelligent class of men. God is God eternally, and an ordinary living entity is eternally a part and parcel of God. God is one without a second, and the ordinary living entities are many without number. All such living entities are maintained by God Himself, and that is the verdict of the Vedic literatures. When Krsna was on the lap of His mother, the demon Putana appeared before His mother and prayed to nurture the child in her lap. Mother Yasoda agreed, and the child was transferred onto the lap of Putana, who was in the garb of a respectable lady. Putana wanted to kill the child by smearing poison on the nipple of her breast. But when everything was complete, the Lord sucked her breast along with her very air of life, and the demon’s gigantic body, said to be as long as six miles, fell down. But Lord Krsna did not need to expand Himself to the length of the she-demon Putana, although He was quite competent to extend Himself more than six miles long. In His Vamana incarnation He posed Himself as a dwarf brahmana, but when He took possession of His land, promised by Bali Maharaja, He expanded His footstep to the top of the universe, extending over thousands and millions of miles. So it was not very difficult for Krsna to perform a miracle by extending His bodily feature, but He had no desire to do it because of His deep filial love for His mother, Yasoda. If Yasoda had seen Krsna in her lap extending six miles to cope with the she-demon Putana, then the natural maternal love of Yasoda would have been hurt because in that way Yasoda would have come to know that her so-called son, Krsna, was God Himself. And with the knowledge of the Godhood of Krsna, Yasodamayi would have lost the temper of her love for Krsna as a natural mother. But as far as Lord Krsna is concerned, He is God always, either as a child on the lap of His mother, or as the coverer of the universe, Vamanadeva. He does not require to become God by undergoing severe penances, although some men think of becoming God in that way. By undergoing severe austerities and penances, one cannot become one or equal with God, but one can attain most of the godly qualities. A living being can attain godly qualities to a large extent, but he cannot become God, whereas Krsna, without undergoing any type of penance, is God always, either in the lap of His mother or growing up or at any stage of growth.
So at the age of only three months He killed the Sakatasura, who had remained hidden behind a cart in the house of Yasodamayi. And when He was crawling and was disturbing His mother from doing household affairs, the mother tied Him with a grinding pestle, but the naughty child dragged the pestle up to a pair of very high arjuna trees in the yard of Yasodamayi, and when the pestle was stuck between the pair of trees, they fell down with a horrible sound. When Yasodamayi came to see the happenings, she thought that her child had been saved from the falling trees by the mercy of the Lord, without knowing that the Lord Himself, crawling in her yard, had wreaked the havoc. So that is the way of reciprocation of love affairs between the Lord and His devotees. Yasodamayi wanted to have the Lord as her child, and the Lord played exactly like a child in her lap, but at the same time played the part of the Almighty Lord whenever it was so required. The beauty of such pastimes was that the Lord fulfilled everyone’s desire. In the case of felling the gigantic arjuna trees, the Lord’s mission was to deliver the two sons of Kuvera, who were condemned to become trees by the curse of Narada, as well as to play like a crawling child in the yard of Yasoda, who took transcendental pleasure in seeing such activities of the Lord in the very yard of her home.
The Lord in any condition is Lord of the universe, and He can act as such in any form, gigantic or small, as He likes.