Shatapatha Brahmana 13.1.3.1

13.1.3.1

yathā vai haviṣo'hutasya skandet evametatpaśo skandati yaṃ niktamanālabdhamutsṛjanti yatstokīyā juhoti sarvahutamevainaṃ juhotyaskandāyāskannaṃ hi tadyaddhutasya skandati sahasraṃ juhoti sahasrasammito vai svargo lokaḥ svargasya lokasyābhijityai

Even as some of the havis (offering-material) may be spilled before it is offered, so also (part) of the victim is here spilled in that they let loose the sprinkled (horse) before it is slain. When he offers the Stokîyâs (oblations of drops), he offers that (horse) as a complete offering --so as to make good any spilling; for unspilled is any (part) of the offered (material) that is spilled. A thousand (oblations of drops) he offers for the obtainment of the heavenly world, for the heavenly world is equal in extent to a thousand.