443.Abu Dharr reported that the Messenger of Allah told his companions that "...in man's sexual intercourse (with his wife) there is Sadqa (charity)." They (the companions) said: Messenger of Allah, is there a reward for him who satisfied 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."
(Muslim).
(Ideal Woman in Islam. by Imran Muhammad).