The second sedra in Bamidbar is Naso, the longest and, for me, the most problematic sedra in the Torah. It has several themes relating to purity (or impurity).
It starts with the census of the Levitical families for the tasks of the Mishkan and then suddenly, without warning, comes the law of the Sotah. This is the Law relating to the faithless wife or, rather, the wife of a jealous husband who believed but had no evidence that his wife had been unfaithful, or who might simply have had a grudge against her. In order to prove her innocence, she was taken to the Cohen and, in public, made to drink ‘the waters of bitterness’