Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 15

Sanskrit:

तस्यावनिज्य चरणौ तदप: स्वमूर्ध्नाबिभ्रज्जगद्गुरुतमोऽपि सतां पतिर्हि ।ब्रह्मण्यदेव इति यद्गुणनाम युक्तंतस्यैव यच्चरणशौचमशेषतीर्थम् ॥ १५ ॥

ITRANS:

tasyāvanijya caraṇau tad-apaḥ sva-mūrdhnābibhraj jagad-gurutamo ’pi satāṁ patir hibrahmaṇya-deva iti yad guṇa-nāma yuktaṁtasyaiva yac-caraṇa-śaucam aśeṣa-tīrtham

Translation:

The Lord bathed Nārada’s feet and then put the water on His own head. Although Lord Kṛṣṇa is the supreme spiritual authority of the universe and the master of His devotees, it was proper for Him to behave in this way, for His name is Brahmaṇya-deva, “the Lord who favors the bṛāhmaṇas.” Thus Śrī Kṛṣṇa honored the sage Nārada by bathing his feet, even though the water that bathes the Lord’s own feet becomes the Ganges, the ultimate holy shrine.

Purport:

Since Lord Kṛṣṇa’s own lotus feet are the source of the most holy Ganges, the Lord did not have to purify Himself by bathing Nārada Muni’s feet. Rather, as Śrīla Prabhupāda explains: “Lord Kṛṣṇa in Dvārakā enjoyed the pastimes of a perfect human being. When, therefore, He washed the feet of the sage Nārada and took the water on His head, Nārada did not object, knowing well that the Lord did so to teach everyone how to respect saintly persons.”