Shatapatha Brahmana 11.1.5.4

11.1.5.4

so'dyāmāvāsyeti manyamāna upavasati athaiṣa paścāddadṛśe tadyajamāno yajñapathādeti tadāhuḥ kathaṃ kuryāditvā yajñapathādyajetā3 na yajetā3 iti yajeta haiva na hyanyadapakramaṇam bhavati śvaḥ śva evaiṣa jyāyānudeti sa āmāvāsyavidhenaiveṣṭvātheṣṭimanunirvapati tadaharvaiva śvo vā

He keeps the fast thinking, 'To-day is the day of new moon;' and then that (moon) is seen in the west, and the Sacrificer departs from the path of sacrifice. As to this they say, 'What should one do when he has departed from the path of the sacrifice? Should he sacrifice, or should he not sacrifice?' He should certainly sacrifice, for there is no other way out of it: day after day that (moon) rises larger. Having performed offering after the manner of the New-moon sacrifice, he takes out material for an additional offering either on the same, or on the following day.