Jami` at-Tirmidhi 2611

Narrated Ibn 'Abbas:"A delegation of Abdul-Qais came to the Messenger of Allah (ﷺ) and said: 'We are a tribe from Rabi'ah, and we cannot come to you except during the sacred months. So order us with something that we can take from you, and then we call those who are behind us to it.' So he said: 'I order you with four things: To testify to La Ilaha Illallah, and that I am the Messenger of Allah; to establish the Salat, to give the Zakat, and to give the Khumus from the spoils of war that you gain