«كان إذا أراد أن يباشر امرأة من نسائه وهي حائض أمرها أن تأتزر ثم يباشرها»
It was the practice of the Prophet (peace and blessings be upon him):
"When he (peace and blessings be upon him) intended to be intimate with one of his wives while she was menstruating, he would instruct her to wrap a waist-cloth (izar) around herself, and then he would be intimate with her."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 4653