2 Samuel 16:20-22

20Then Absalom said to Ahithophel, ‘What do you think that we should do now? What is your advice?’

21Ahithophel answered, ‘Sleep with your father's slave wives that are here. He left them to take care of his palace. Then all the people in Israel will know that you have insulted your father. They will know that he must now hate you. That will help your own men to be strong.’

22So they put up a tent for Absalom on the roof of the palace. There he had sex with his father's slave wives, and all the Israelites could see him.