Śatapatha Brāhmaṇa ("of a hundred paths") 1.3.1.11

1.3.1.11

taddhaike | srukṣammārjanānyagnāvabhyādadhati vedasyāhābhūvantsruca ebhiḥ samamārjiṣuridaṃ vai kiṃcidyajñasya nedidam bahmā aśanamāharettam pātranirṇejanam pāyayedevaṃ tattasmādu parāsyedevaitāni

Here now some throw the grass-ends used for cleaning the spoons into the (Âhavanîya) fire. 'To the veda (grass-bunch) they assuredly belonged, and the spoons have been cleaned with them: hence it is something that belongs to the sacrifice, and (we throw it into the fire) in order that it should not become excluded from the sacrifice,' thus (they argue). Let him, however, not do so, since he would thereby make him to whom he will offer food, drink the slops of the vessels. Let him therefore throw them away (on the heap of rubbish).