231.Some of the Companions ¹⁷) of the Messenger of Allah (peace be upon him) said to the Prophet:(peace be upon him) O Messenger of Allah, the affluent have made off with the rewards: they pray as we pray, they fast as we fast, and they give away in charity the superfluity of their wealth. The Prophet (peace be upon him) said: Has not Allah made things for you to give away in charity? Truly every tasbiha ¹⁸) is a charity every takbira ¹⁹) is a charity, every tahmida ²⁰) is a charity and every tahlia ²¹) is a charity; to enjoin a good action is a charity, to forbid an evil action is a charity and in a sexual act each of you there are a charity. They said: O Messenger of Allah, when one of us fulfils his sexual desire will he have some reward for that? The Prophet (peace be upon him) said: Do you [not] think that were he to act upon it unlawfully he wold be sinning? Likewise, if he has acted upon it lawfully he will have a reward.
(Muslim).
(Forty Hadith translated by. Ezzedin Ibrahim and Denys Johnson-Davies).