Amr (may Allah be pleased with him) wrote: "As-salamu alaykum" (Peace be upon you) and "Amma ba'd" (To proceed)! Here I am at your service; camels are coming to you, the first of them will be with you and the last with me, with the hope that I will find a way by sea. When the first camels arrived, Umar (may Allah be pleased with him) called Zubayr (may Allah be pleased with him) and said: Take these first camels towards Najd, and send to me every household that you are able to send to me. And whoever you are unable to send, then order for each household a camel with what it carries, and order them to wear two garments, and to slaughter the camel, melt down its fat, cut its meat into strips and dry it, and make shoes from its hide. Then let them take a bundle of the dried meat, a bundle of the fat and a bowl of flour, and cook and eat, until Allah Almighty brings them provision. But Zubayr (may Allah be pleased with him) refused to go out. Umar (may Allah be pleased with him) said: By Allah! You will not find the like of this (opportunity) until you depart from this world. Then he called another man, I think it was Talhah (may Allah be pleased with him); he too refused. Then he called Abu Ubaydah bin al-Jarrah (may Allah be pleased with him), and he went out on that mission. The rest of the hadith is similar.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 13017