Śatapatha Brāhmaṇa ("of a hundred paths") 4.5.4.7

4.5.4.7

mādhyandine vaināntsavane gṛhṇīyāt | ukthyaṃ gṛhītvopākariṣyanvā pūtabhṛto 'yaṃ ha vā asyaiṣo 'nirukta ātmā yadukthyaḥ so eṣā mīmāṃsaiva prātaḥsavana evaināngṛhṇīyādāgrayaṇaṃ gṛhītvā

Or he might draw them from the Pûtabhrit, at the midday pressing, after drawing the Ukthya, or when about to bespeak (the chant), for the Ukthya indeed is the same as that undefined self of his. But this is mere speculation: let him rather draw them at the morning pressing, after drawing the Âgrayana.