Mantra 1

अथ यां तृतीयां जुहुयात्तां जुहुयादपानाय स्वाहेत्यपानस्तृप्यति ॥ ५.२१.१ ॥

In plain words

The third offering that he makes, let him make with the words "To the down-breath, svāhā." Then the down-breath is satisfied.