Shatapatha Brahmana 14.1.3.24

14.1.3.24

atha dakṣiṇata uttānena pāṇinā nihnute viśvābhyo mā nāṣṭrābhyaspāhīti sarvābhyo mārtibhyo gopāyetyevaitadāha yajñasya śīrṣacinnasya [raso vyakṣaratsa] pitṝ!nagacattrayā vai pitarastairevainametatsamardhayati kṛtsnaṃ karoti

On the right (south) side (of the Mahâvîra) he (the Sacrificer) then makes amends by (laying down) the hand with the palm upwards, with, 'Shield me from all evil spirits!' whereby he means to say, 'Protect me from all troubles!' When the sacrifice had its head cut off, its life-sap flowed away, and went to the Fathers, but the Fathers are three in number: it is with these that he thus supplies and completes it (the Pravargya).