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, this tribe of Rabi'ah, the disbelievers of Mudar stand between us and you, so we can reach you only in a sacred month. Give us a command that we may adopt and to which we may invite those behind us. He (peace and blessings be upon him) said: "I command you with four things and forbid you four: faith in Allah, bearing witness that there is no god except Allah," and he (peace and blessings be upon him) counted on his hand by tying knots with his fingers, "establishing prayer, paying zakah, fasting Ramadan, and that you pay the khumus (one-fifth) of whatever spoils you gain. And I forbid you the dubba', the hantam, the naqir and the muzaffat."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12894