Brihadaranyaka Upanishad 3.1.4

3.1.4

yājñavalkyeti hovāca yadidam̐sarvamahorātrābhyāmāptam̐ sarvamahorātrābhyāmabhipannaṃ kena yajamāno'horātrayorāptimatimucyata ityadhvaryuṇartvijā cakṣuṣādityena cakṣurvai yajñasyādhvaryustadyadidaṃ cakṣuḥ so'sāvādityaḥ so'dhvaryuḥ sa muktiḥ sātimuktiḥ

'Yâgñavalkya,' he said, 'everything here is reached by day and night, everything is overcome by day and night. By what means then is the sacrificer freed beyond the reach of day and night?'
Yâgñavalkya said: 'By the Adhvaryu priest, who is the eye, who is Âditya (the sun). For the eye is the Adhvaryu of the sacrifice, and the eye is the sun, and he is the Adhvaryu. This constitutes freedom, and perfect freedom.'