SB 8.18.14
tasyopaniyamanasya
savitrim savitabravit
brhaspatir brahma-sutram
mekhalam kasyapo ’dadat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
At the sacred thread ceremony of Vamanadeva, the sun-god personally uttered the Gayatri mantra, Brhaspati offered the sacred thread, and Kasyapa Muni offered a straw belt.