It is narrated from Sayyiduna Adi bin Hatim (may Allah be pleased with him): I came to Sayyiduna Umar (may Allah be pleased with him) with some people of my tribe. He began assigning stipends of two thousand to men of (the tribe of) Tayyi', and turned away from me. So I said: O Commander of the Believers! Do you know me? Adi said: He laughed until he fell back, and said: Yes, by Allah, I know you. You believed when they disbelieved, you came forward when they turned their backs, and you were loyal when they betrayed. The first sadaqah that made the face of the Messenger of Allah (peace and blessings be upon him) and the faces of his Companions shine was the sadaqah of (the tribe of) Tayyi', which you brought to the Messenger of Allah (peace and blessings be upon him). Then he began to apologise and said: I have only assigned (stipends) to people whom poverty has crushed, and they are the needy of their clans, because of the obligations that fall upon them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13143