Śatapatha Brāhmaṇa ("of a hundred paths") 2.1.4.20

2.1.4.20

eṣa u vai prāṇaḥ | taṃ vai tathaiva hareyuryathainameṣa pratyaṅṅupācaretpratyaṅ haivainam prāṇaḥ praviśatyatha yasmātparāṅ bhavati parāṅu haivāsmātprāṇo bhavati sa yo hainaṃ tatrānuvyāharetparāṅsmātprāṇo 'bhūditīśvaro ha yattathaiva syāt

Moreover, that (fire) is the (sacrificer's) breath: let them therefore carry it in such wise that it turns back towards him; for it is in the direction of him that the breath enters into him. And, verily, from whomsoever it (the fire) turns away, from him the breath also turns away; and if in that case any one were to curse him, saying, 'May the breath turn away from him!' then he would indeed be liable to fare thus.