The 223rd mitzvah is that we are commanded regarding the law of a sotah.1

The source of this commandment is G‑d's statement,2 "If a man's wife is suspected of committing adultery...."

All the details of this mitzvah — how one makes her drink [the special water used to determine her innocence or guilt], how her sacrifice is offered, and other conditions that apply to her — are found in the tractate devoted to this subject, tractate Sotah.