yājñavalkyaḥ - Yājñavalkya; tataḥ - thereafter; brahman - O brāhmaṇa; chandāṁsi - mantras; adhi - additional; gaveṣayan - seeking out; guroḥ - to his spiritual master; avidyamānāni - not known; su-upatasthe - he carefully worshiped; arkam - the sun; īśvaram - the powerful controller.

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.