Srimad-Bhagavatam: Canto 8 - Chapter 1 - Verse 14
Sanskrit:
तस्योपनीयमानस्य सावित्रीं सविताब्रवीत् ।बृहस्पतिर्ब्रह्मसूत्रं मेखलां कश्यपोऽददात् ॥ १४ ॥
ITRANS:
tasyopanīyamānasyasāvitrīṁ savitābravītbṛhaspatir brahma-sūtraṁmekhalāṁ kaśyapo ’dadāt
Translation:
At the sacred thread ceremony of Vāmanadeva, the sun-god personally uttered the Gāyatrī mantra, Bṛhaspati offered the sacred thread, and Kaśyapa Muni offered a straw belt.