Sentence:  So the men change along my changeless stream,/ And change their faiths; but I yield all alike/ Sweet water for their drinking, sweet as wine,/ And pure sweet water for their <WSD>lustral</WSD> rites:/ For thirty generations of my corn/ Outlast a generation of my men,/ And thirty generations of my men/ Outlast a generation of their gods. 
Meaning of the word marked with <WSD> tags:  Of or pertaining to (ritual) purification.