Imam Aba Abdillah al Sadiq (as) was asked about coming to women from their rear (i.e; in their anus).
Imam (as) said : She is a doll, do not hurt her.
Safwan ibn Yahya once said to Imam Reza (as) that one of his followers has asked me to ask you a question in which he feels scared and shy.
Imam (as) asked : What is the question?
Safwan ibn Yahya said : Can a man have anal intercourse with his wife?
Imam (as) replied : It is up to him.
Safwan ibn Yahya then asked : Do you do so?
Imam (as) replied : No, we do not do so.
Divine Treasure 