SB 12.6.66
yajñavalkyas tato brahmams
chandamsy adhi gavesayan
guror avidyamanani
supatasthe ’rkam isvaram
Translation:
My dear brahmana Saunaka, Yajñavalkya then desired to find out new yajur-mantras unknown to even his spiritual master. With this in mind he offered attentive worship to the powerful lord of the sun.