Bible Notes Online - Leviticus 15 - ESV
Commentary

The theme continues, that God is holy, and man frequently is not. Even 'ordinary' bodily discharges make a man or woman unclean; something that is common to man is not necessarily right. No wonder the Scripture says that even the stars are not pure in His sight. This chapter explains this uncleanness. At the same time, these rules, and others, provide a routine for basic healthy living.

v4-12: Uncleanness spreads; worldliness, wrong attitudes, rebellion, complacency, and more. This is echoed in Hag 2.10-14 concerning the nation of Judah, which had just returned from exile.

v13-15: Atonement was necessary; not just the washing of hands which was sufficient for some (v11), nor just the washing of clothes which was sufficient for others (v7-8); the man had to come with an offering to the Lord.

v25: In Mark 5.25, where the woman suffered in this way for several years, she remained unclean.

v31: The reasons for these regulations; that the Israelites might be ceremonially clean, especially in regard to their worship of God ("my dwelling place"). There is real common sense here also.