SB 10.14.37

prapañcaṁ niṣprapañco ’pi
 viḍambayasi bhū-tale
prapanna-janatānanda-
 sandohaṁ prathituṁ prabho
Word for word: 
prapañcam — that which is material; niṣprapañcaḥ — completely transcendental to material existence; api — although; viḍambayasi — You imitate; bhū-tale — on the surface of the earth; prapanna — who are surrendered; janatā — of people; ānanda-sandoham — the great variety of different kinds of ecstasies; prathitum — in order to spread; prabho — O master.
Translation: 
My dear master, although You have nothing to do with material existence, You come to this earth and imitate material life just to expand the varieties of ecstatic enjoyment for Your surrendered devotees.
Purport: 

Śrīla Viśvanātha Cakravartī Ṭhākura points out that just as a lamp does not seem to shine as brightly in sunlight as it does in the shade, or as a diamond does not seem as brilliant on a silver platter as it does on a plate of blue glass, the Lord’s pastimes as Govinda do not seem as amazing in the transcendental abode of Vaikuṇṭha as they do within the material realm of Māyā. Lord Kṛṣṇa comes to the earth and acts toward His pure devotees exactly like a devoted son, boyfriend, husband, father, friend and so on, and within the darkness of material existence these brilliant, liberated pastimes give unlimited ecstasy to the surrendered devotees of the Lord.

In his Kṛṣṇa, the Supreme Personality of Godhead, Śrīla Prabhupāda quotes Lord Brahmā as follows: “I can also understand that Your appearance as a small cowherd boy, a child of the cowherd men, is not at all a material activity. You are so much obliged by their affection that You are here to enthuse them with more loving service by Your transcendental presence.”