It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) 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 cannot come to you whenever we wish, so tell us what is lawful for us and what is unlawful. He (peace and blessings be upon him) said: "I command you with four things and forbid you four: establish prayer, pay zakah, fast Ramadan, and give the khumus (one-fifth) of the spoils of war. And I forbid you the dubba', the hantam, the naqir and the muzaffat."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12899