سنن النسائي

It was narrated that Ibn 'Abbas said: "The delegation of 'Abdul-Qais came to the Messenger of Allah (ﷺ) [SAW] and said: 'We are a group of people from (the tribe of) Rabi'ah, and we can only reach you during the sacred month. Tell us something that we can take from you and to which we may call those who are behind us.' He said: 'I command you to do four things and I forbid you from four: Faith in Allah'- and he explained that to them- 'bearing witness that there is none worthy of worship except Allah, establishing Salah, paying Zakah, and giving me one-fifth (the Khumus) of the spoils of war you acquire. And I forbid you from Ad-Dubba', Al-Hantam, Al-Muqayyir, and Al-Muzaffat.'"