Shatapatha Brahmana 11.1.4.1

11.1.4.1

taddhaike dṛṣṭvopavasanti śvo nodetetyabhrasya vā hetoranirjñāya vāthotopavasantyathainamutābhyudeti sa yadyagṛhītaṃ havirabhyudiyātprajñātameva tadeṣaiva vratacaryā yatpūrvedyurdugdhaṃ dadhi havirātañcanaṃ tatkurvanti pratipramuñcanti vatsāṃstānpunarapākurvanti

Now, some people enter upon the fast when they (still) see (the moon, on the fourteenth day of the half-month), thinking, 'To-morrow he will not rise,'--either on account of clouds or not having ascertained properly, they enter upon the fast, and (in the morning) he rises over him. Now if he (the moon) should rise on (the material for) the oblation being not yet taken out, then that approved (procedure is followed) and the same fasting-observance. The sour curds from last night's milking they use for coagulating the sacrificial food; they let the calves join (their mothers), and drive them away again.