Sayyiduna Ibn Abbas (may Allah be pleased with them both) relates: The delegation of Abd al-Qays came to the Messenger of Allah (peace and blessings be upon him) and said: O Messenger of Allah, the disbelievers of Mudar stand between us and you, and we can reach you only in the sacred months, so give us a command to which we may hold fast and to which we may invite those behind us. The Messenger of Allah (peace and blessings be upon him) said: "Four things, and four: bearing witness that there is no god except Allah and that Muhammad is His servant and Messenger, establishing prayer, paying zakah, fasting Ramadan, and paying the khumus (one-fifth) of whatever spoils you gain. And I forbid you the nabidh of the dubba', the hantam, the naqir and the muzaffat."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12896