Sayyiduna Ibn Abbas (may Allah be pleased with them both) relates that the delegation of Abd al-Qays came to the Prophet (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 a sacred month, so tell us what is lawful for us and what is unlawful for us. He (peace and blessings be upon him) said: "I command you with one thing and forbid you four. I command you to bear witness that there is no god except Allah, and to establish prayer, pay zakah, fast Ramadan, and give 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 / 12900