Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: When Sayyiduna Umar (may Allah be pleased with him) was wounded, I was the first person to come. He said: Remember three things from me, for I fear that the people will not be able to reach me. The first is that I have not given any ruling about kalalah, I am not appointing anyone as caliph over the people, and every slave of his shall be counted free.
Ahmad recorded it, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الفرائض / 7162