If the sacrifice is injured by the Sâma-veda side, let him offer a libation in the Âhavanîya fire, saying, Svah, Svâhâ! Thus does he bind together and heal, by means of the essence and the power of the Sâman verses themselves, whatever break the Sâman sacrifice may have suffered.

In plain words: If a mistake happens in the Sama Veda part of the ritual, the priest should pour an offering into the eastern offering fire, saying 'Svah, Svaha!' This uses the power of the Sama verses to repair the mistake.