Abdullah bin Umar reported,
The Messenger of Allah ﷺ wrote the document concerning charity, but he did not send it out to his agents before he passed away, so he kept it attached to his sword. After he died, Abu Bakr 
acted upon it until he died, then Umar until he died. It stated that for every five camels a sheep is due, for ten camels two sheep, for fifteen three sheep, for twenty four sheep, and for twenty-five a she-camel in her second year.Abdullah bin Ahmad said, "My father said, 'Then an illness came over me while I was in the gathering of Abbad bin Awwam, and I wrote down the rest of the hadith, but I think I did not grasp part of it, so I had doubts about the remainder of the hadith and left it out.'"
Ahmad 4633
Sahihبهذا الحديث في المسند في حديث الزهري عن سالم لأنه كان قد جمع حديث الزهري عن سالم فحدثنا به في حديث سالم عن محمد بن يزيد بتمامه وفي حديث عباد عن عباد بن العوام
This is a clarification from Abdullah bin Ahmad, showing us something of what his father used to do in narrating the Musnad to them, namely that he collected the reports according to the shaykhs at the start of his work. That is why he narrated to them with the preceding chain, in what he had collected of the hadith of Zuhri from Salim, and then he narrated to them with the following chain as well.The first one he narrated to them from Abbad bin Awwam, leaving out part of it, while the last one he narrated to them from Muhammad bin Yazid in full, since nothing arose that prevented him from hearing all of it, memorizing it, and writing it down.