Shatapatha Brahmana 3.8.4.9

3.8.4.9

tena purastādanuyājeṣu carati | sa yo 'yam purastātprāṇastamevaitaddadhāti tena paścādupayajati sa yo 'yam paścātprāṇastamevaitaddadhāti tāvimā ubhayataḥ prāṇau hitau yaścāyamupariṣṭādyaścādhastāt

Therewith he (the Adhvaryu) performs in front (on the Âhavanîya) at the after-offerings,---whereby he puts into (the victim) that vital air which is here in front;--and therewith he (the Pratiprasthâtri) performs behind (the altar) at the by-offerings,--whereby he puts into it that vital air which is here behind: thus two vital airs are here contained (or beneficial) on both sides, the one above and the one below.