Leviticus 15:19-24

Lev 15:19 “When a woman has a discharge, and the discharge in her body is blood, she will be in her menstrual impurity for seven days, and whoever touches her will be contaminated until the evening.
Lev 15:20 And everything on which she lies during her menstrual impurity will be contaminated. Everything also on which she sits will be contaminated.
Lev 15:21 And whoever touches her bed will wash his clothes and bathe himself in water and be contaminated until the evening.
Lev 15:22 And whoever touches any container on which she sits will wash his clothes and bathe himself in water and be contaminated until the evening.
Lev 15:23 Whether it is the bed or any container on which she sits, when he touches it he will be contaminated until the evening.
Lev 15:24 And if any man lies with her and her menstrual impurity comes upon him, he will be contaminated seven days, and every bed on which he lies will be contaminated.

what contaminates

Anyone within the covenant community — male or female — would be ceremonially unclean if something discharged from his or her body. Jesus taught his disciples that true contamination happens because evil within the heart comes out (Matthew 15:10-20). These rules concerning contamination due to discharge were to be a reminder of that spiritual truth.

A woman’s menstrual cycle is a very normal and healthy thing, and there is nothing evil about it. But in the old covenant community, this time became a time for her to focus on her relationship with God, and declare her devotion to Him.

LORD, show us how to separate ourselves for you, and not to allow our own hearts to defile us.