He should proceed thus: Having taken a water-pot or a water-jar he should go pouring it out from the garhapatya to the ahavaniya with the verse: Here Visnu strode. The rc [RigVeda verse, e.g. 1.22.17] is a divine purification, water is a divine purification. Whatever here is unappeased of the sacrifice and whatever is impure, for all that, water forms the means of appeasing. So by water they appease it.