Śatapatha Brāhmaṇa ("of a hundred paths") 2.1.4.8

2.1.4.8

taddhaike 'nudite mathitvā | tamudite prāñcamuddharanti tadu tadubhe ahorātre parigṛhṇīmaḥ prāṇodānayormanasaśca vācaśca paryāptyā iti vadantastadu tathā na kuryādubhau haivāsya tathānudita āhitau bhavato 'nudite hi mathitvā tamudite prāñcamuddharanti sa ya udita āhavanīyam manthetsa ha tatparyāpnuyāt

Now some churn (the fire) before sunrise and take it eastwards (from the Gârhapatya to the Âhavanîya) after sunrise, arguing that thereby they secure both the day and the night for the obtainment of out-breathing and in-breathing, of mind and speech. But let him not do so; for when they thus churn (the fire) before sunrise, and take it eastwards after sunrise, both his (fires) are in reality set up before sunrise. By churning the Âhavanîya after sunrise he will obtain that (combination of blessings).