Śatapatha Brāhmaṇa ("of a hundred paths") 4.5.3.11

4.5.3.11

athetya stotramupākaroti | somo 'tyarecyupāvartadhvamityatyevainametadrecayati taṃ vai purāstamayādupākarotyastamite 'nuśaṃsati tadenenāhorātre saṃdadhāti tasmātpurāstamayādupākarotyastamite 'nuśaṃsati

Thereupon he returns (to the sadas) and bespeaks the chant with, 'Soma has been left over: Turn ye back!' for he indeed causes it to remain over by that (Shodasin graha). He (the Adhvaryu) bespeaks it before the setting of the sun; and after sunset he (the Hotri) follows it up by reciting the sastra: thus he thereby joins day and night together,--therefore he bespeaks (the stotra) before the setting of the sun, and after sunset he follows it up by reciting the sastra.