Narrated Abdullah ibn Abbas:
Al-Hasan said: Ibn Abbas preached towards the end of Ramadan on the pulpit (in the mosque) of al-Basrah. He said: Bring forth the sadaqah relating to your fast. The people, as it were, could not understand. Which of the people of Medina are present here? Stand for your brethren, and teach them, for they do not know.
The Apostle of Allah (peace_be_upon_him) prescribed this sadaqah as one sa' of dried dates or barley, or half a sa' of wheat