John Calvin Commentary Leviticus 15:19

"And if a woman have an issue, [and] her issue in her flesh be blood, she shall be in her impurity seven days: and whosoever toucheth her shall be unclean until the even." — Leviticus 15:19 (ASV)

And if a woman have an issue. Women are now spoken of who suffer under a twofold issue of blood; for with almost all of them it occurs every month, (from which it is called menses, or menstruation,), and some suffer from a constant hemorrhage. He declares both to be unclean. After menstruation, a certain period of separation is appointed, during which the law prohibited their cohabitation with men; but if the blood flowed beyond the usual time, the time of purification is postponed until it ceased.

From this it appears that in every shameful thing the Jews were reminded of their uncleanness, so that they might become accustomed to modesty and seek purity.

And this appears even more clearly at the end of the chapter, where it is said (verse 31): Thus shall you separate the children of Israel from their uncleanness; that they do not die—when they defile My tabernacle. God, I say, briefly sets forth His intention that He would drive away all profanation far from His people; because He desires sincerity to prevail among His worshippers and cannot bear His tabernacle to be polluted by any stain.