Leviticus 18:19

“Speak to the sons of Israel, saying: ‘When a woman gives birth and bears a male child, then she shall be unclean for seven days, as in the days of her menstruation she shall be unclean.

‘If a man actually lies with her so that her menstrual impurity is on him, he shall be unclean seven days, and every bed on which he lies shall be unclean.

‘If there is a man who lies with a menstruous woman and uncovers her nakedness, he has laid bare her flow, and she has uncovered the flow of her blood; thus both of them shall be cut off from among their people.

Then David sent messengers and took her, and she came to him, and he lay with her; and when she had purified herself from her uncleanness, she returned to her house.

“In you they have uncovered their fathers’ nakedness; in you they have humbled her who was unclean in her menstrual impurity.

but that we write to them that they abstain from things contaminated by idols and from sexual immorality and from what is strangled and from blood.