Musannaf Ibn Abi Shayba 28:503

Mu'adh ibn Mu'adh narrated to us, he said: Ibn 'Awn narrated to us, he said: A man from Banu Zurayq narrated to us, he said: Abu Bakr granted Talha a piece of land and wrote a document for him regarding it, and he had witnesses testify to it, among them Umar. So Talha brought the document to Umar and said, "Seal this." He (Umar) said, "I will not seal it. This is for you to the exclusion of the people." So Talha went away angry and came to Abu Bakr and said, "By Allah, I do not know whether you are the Caliph or Umar." He (Abu Bakr) said, "No, rather it is Umar, but he refused."