Shatapatha Brahmana 3.8.1.10

3.8.1.10

tadāhuḥ | naiṣa yajamānenānvārabhyo mṛtyave hyetaṃ nayanti tasmānnānvārabheteti tadanvevārabheta na vā etam mṛtyave nayanti yaṃ yajñāya nayanti tasmādanvevārabheta yajñādu haivātmānamantariyādyannānvārabheta tasmādanvevārabheta tatparo 'kṣamanvārabdham bhavati vapāśrapaṇībhyām pratiprasthātā pratiprasthātāramadhvaryuradhvaryuṃ yajamāna etadu paro 'kṣamanvārabdham bhavati

As to this they say, 'That (victim) must not be held on to by the sacrificer, for they lead it unto death; therefore let him not hold on to it.' But let him nevertheless hold on to it; for that (victim) which they lead to the sacrifice they lead not to death; therefore let him hold on to it. Moreover he would cut himself off from the sacrifice, were he not to hold on to it; therefore let him hold on to it. It is held on to in a mysterious way; by means of the spits the Pratiprasthâtri (holds on to it); to the Pratiprasthâtri the Adhvaryu, to the Adhvaryu the Sacrificer; thus then it is held on to in a mysterious way.