Musnad Ahmad 1153:606

Ali ibn Ishaq narrated to us, he said: Abdullah informed us, he said: Al-Awza'i informed us, he said: Shaddad Abu 'Ammar narrated to me, from Aisha: "That women from the people of Basra entered upon her, so she ordered them to perform istinja (cleaning the private parts) with water." And she said: "Order your husbands to do that, for the Prophet, peace and blessings of Allah be upon him, used to do it." "And it is a cure for hemorrhoids." (Aisha said it, or Abu 'Ammar said it).