Śatapatha Brāhmaṇa ("of a hundred paths") 3.9.2.6

3.9.2.6

divā gṛhṇīyāt | paśyanyajñasya rasaṃ gṛhṇānīti tasmāddivā gṛhṇīyādetasmai vai gṛhṇāti ya eṣa tapati viśvebhyo hyenā devebhyo gṛhṇāti raśmayo hyasya viśve devāstasmāddivā gṛhṇīyāddiveva vā eṣa tasmādveva divā gṛhṇīyāt

Let him take it by day, thinking, 'Seeing, I will take the sap of the sacrifice:' therefore let him take it by day. For it is for him that burns yonder (the sun) that he takes it, since he takes it for all the gods, and all the gods are his rays of light: therefore let him take it by day. For it is by day alone that he (shines): therefore, then, let him take it by day.