Srimad Bhagavatam Canto 10, Chapter 20, Text 18

SB 10.20.18

dhanur viyati mahendram
 nirgunam ca guniny abhat
vyakte guna-vyatikare
 ’gunavan puruso yatha
When the curved bow of Indra [the rainbow] appeared in the sky, which had the quality of thundering sound, it was unlike ordinary bows because it did not rest upon a string. Similarly, when the Supreme Lord appears in this world, which is the interaction of the material qualities, He is unlike ordinary persons because He remains free from all material qualities and independent of all material conditions.
Srila Prabhupada comments as follows: “Sometimes, in addition to the roaring thunder of the clouds, there is an appearance of a rainbow, which stands as a bow without a string. Actually, a bow is in the curved position because it is tied at its two ends by the bowstring; but in the rainbow there is no such string, and yet it rests in the sky so beautifully. Similarly, when the Supreme Personality of Godhead descends to this material world, He appears just like an ordinary human being, but He is not resting on any material condition. In the Bhagavad-gita, the Lord says that He appears by His internal potency, which is free from the bondage of the external potency. What is bondage for the ordinary creature is freedom for the Personality of Godhead.”
Srimad Bhagavatam Canto 10, Chapter 20, Text 17
Srimad Bhagavatam Canto 10, Chapter 20, Text 19