My dear brāhmaṇa Śaunaka, Yājñavalkya 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.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
याज्ञवल्क्यस्ततो ब्रह्मंश्छन्दांस्यधिगवेषयन् । गुरोरविद्यमानानि सूपतस्थेऽर्कमीश्वरम्
yājñavalkyastato brahmaṃśchandāṃsyadhigaveṣayan | guroravidyamānāni sūpatasthe'rkamīśvaram
SB 12.6.66