Khuzaymah ibn Thabit narrated in Mishkat A-Masabih #3192
The Prophet sallallahu alayhe wa sallam said, "Allah is not ashamed of the truth. Do not have intercourse with women through the anus." Ahmad, Tirmidhi, Ibn Majah and Darimi transmitted it.
AbuHurayrah narrated in Mishkat Al-Masabih #0551 Allah's Messenger sallallahu alayhe wa sallam said, He who comes to a menstruating woman, or to a woman from her backside (for sexual intercourse), or to a kahin (soothsayer), he disbelieved that which was revealed to Muhammad.
Transmitted by Tirmidhi. In Ibn Majah and Darimi's version it says: Kahin, believing what he says, he committed Kufr.
AbuDharr said in Sahih Muslim#2198 Some of the people from among the companions of the Apostle of Allah sallallahu alayhe wa sallam said to him: Messenger of Allah, the rich have taken away (all the) reward. They observe prayer as we do, they keep the fasts as we keep them, and they give sadaqah from their surplus riches. Upon this he (the Holy Prophet) said: Has Allah not prescribed for you (a course) by following which you can (also) do sadaqah? In every declaration of the glorification of Allah (i.e. saying SubhanAllah) there is a sadaqah, every Takbir (i.e. saying AllahuAkbar) is a sadaqah, every praise of Him (saying Alhamdulillah) is a sadaqah, every declaration that He is One (La ilaha illallah) is sadaqah, enjoining of good is a sadaqah, forbidding of that which is evil is a Sadaqah, and in man's sexual intercourse (with his wife) there is a Sadaqah.  They (the companions) said: Messenger of Allah, is there reward for him who satisfies his sexual passion among us?  He said: Tell me, if he were to devote it to something forbidden, would it not be a sin on his part? Similarly, if he were to devote it to something lawful, he should have a reward.
  Bibliography

Ahmad,Luqman, The Necessity For Guardianship in Marriage Madison WI, Al-Jumuha, The Islamic Revival Association, Vol. 8 #2 1417
Al-Jumuha What Young People Should Know About The Wedding Night and Beyond, Madison, WI The Islamic Revival Association,  Vol.5 1416
Creed, The Muslim How To Choose A Marriage Partner, Dar Of Islamic Heritage Vol. 4 #6 1996/ 1417
  Philips, Dr. Abu Ameenah Bilal, The Best in Islaam, (Sharjah, UAE, Dar Al Fatah, 1996
Zarabozo, Jamal, Islam A Way of Life and A Movement ,1982


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Excellent  Social Conduct Talks regarding how to the treat wife kindly by Menk