As for your question, we must say that as it has been mentioned in your message, Shaykh Hurr Amili has opened a chapter in his “Wasail al-Shi’ah” entitled “Rules Regarding Anal Intercourse without Ejaculation”. In this chapter, he has quoted three traditions from Shaykh Tusi’s Al-Tahzib. The first tradition forbids anal intercourse when one is observing fast considering it as vaginal intercourse in terms of the rules which are applicable to it. However, the two other traditions imply that anal intercourse is permissible during fast and that, with this action, Ghusl does not become obligatory on the woman. [1] However, according to jurisprudents and religious authorities (Maraje’), sexual intercourse, be it from the back passage or the front, is forbidden and it will render fast void.[2] For further information in this regard, you can refer to index 6085 (Sexual Intercourse during Fast) on our website.
Now when it comes to why some Shia jurisprudents have given such a fatwa in spite of such traditions and how they have reconciled these traditions with other traditions, we shall give the following explanation:
1. Some jurisprudents have criticized the chain of the transmission of the tradition in question saying that it is not reliable and that it should be put aside because the narration is attributed to the Infallible regardless of its being connect.  It is mursal and marfu (elevated)[3]. [4]
2. Some have said that the arguments which consider ghusl-e janabat as a result of insertion (of the male organ) are absolute and unrestricted, so it includes both kinds of the sexual contact.  These jurisprudents have categorically said that these few narrations cannot restrict or limit those absolute traditions. Moreover, the traditions in question are weak and that Shia scholars and jurisprudents have not acted upon them. In fact, they have acted and given fatwa (verdict) against it.[5]
3. Some have said that it is likely that the tradition imply insertion (of male organ) to an extent less than the point of circumcision which does not cause ghusl to become obligatory.[6]
4. Some believe that it is likely that the Infallible (a.s.) had forbidden anal intercourse due to Taqiyah (quietism or dissimulation) because what has been said was in accord with the view of some of the followers of the Sunni school of jurisprudence.[7]
 What was mentioned above have something to do with prohibition of this act for a person who is observing fast. For information about the rules of anal intercourse in situations and times other than the time of fasting, you can refer to index 8627 (Approaching Wife from Behind) on our website.

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