Abu Dharr, radiyallahu 'anhu, reported that some of the Companions of the Messenger of Allah, sallallahu alayhi wasallam, said to him:

"O Messenger of Allah, the rich have taken away all the rewards. They observe the prayer as we do, and they keep the fasts as we do, and they give sadaqah (charity) from their surplus riches." Upon this he (the Prophet) said: "Has Allah not prescribed for you (a course) by following which you can also do sadaqah? Verily in every tasbih (i.e. saying Subhanallah) there is a sadaqah, every takbir (i.e. saying Allahu Akbar) is a sadaqah, every tahmid (i.e. saying Alhamdulillah) is a sadaqah, every tahlil (i.e. saying Lailaha illallah) is a sadaqah, enjoining of good is a sadaqah, forbidding of evil is a sadaqah, and having sexual intercourse with your wife is a sadaqah. They (the Companions) said: "O 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."

[Muslim]