We examine the commentary of Ramban on the beginning of Parashat Hukkat about the strange and perplexing aspects of the “Para Aduma” ritual. We explore ideas in the words of Ramban about the nature of tum’a, the relationship between the Written and Oral Torah, and explanations for the apparent anomalous sacrificing outside the Mikdash, fraught with the dangers of crossing the fine line between Avodat Hashem and Avoda Zara in this setting.  Ramban argues that tum’a is life being overcome by sin, and through the Para Aduma ritual, one drives out sin by reconnecting with God, the Source of purity.