It is narrated from Ibn Sirin (may Allah have mercy on him) that Sayyiduna Anas bin Malik (may Allah be pleased with him) was with Ubaydullah bin Abi Bakrah in a campaign, and they obtained captives. Ubaydullah intended to give Anas (may Allah be pleased with him) a captive before the distribution. Anas (may Allah be pleased with him) said: "No, rather distribute first, then give me from the one-fifth."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12948