Abdullah bin Abbas reported,
When the Messenger of Allah ﷺ passed away and Abu Bakr was appointed caliph, Abbas brought a dispute against Ali concerning certain things left behind by the Messenger of Allah ﷺ.Abu Bakr 
said, "Anything that the Messenger of Allah ﷺ left and did not alter, I will not alter."When Umar became caliph, the two brought their dispute to him, and he said, "Anything that Abu Bakr did not alter, I will not alter."When Uthman became caliph, they brought their dispute to him. Uthman fell silent and lowered his head.Ibn Abbas said, "I feared that he might take it, so I struck my hand between Abbas's shoulders and said, 'Father, I implore you, hand it over to Ali.'"So he handed it over to him.
Ahmad 77
Sahihحدثنا يحيى بن حماد حدثنا أبو عوانة عن الأعمش عن إسماعيل بن رجاء عن عمير مولى العباس
عن ابن عباس قال
لما قبض رسول الله ﷺ واستخلف أبو بكر خاصم العباس عليا في أشياء تركها رسول الله ﷺ فقال أبو بكر رضي الله عنه شيء تركه رسول الله ﷺ فلم يحركه فلا أحركه فلما استخلف عمر اختصما إليه فقال شيء لم يحركه أبو بكر فلست أحركه قال فلما استخلف عثمان رضي الله عنه اختصما إليه قال فأسكت عثمان ونكس رأسه قال ابن عباس فخشيت أن يأخذه فضربت بيدي بين كتفي العباس فقلت يا أبت أقسمت عليك إلا سلمته لعلي قال فسلمه له
Its isnad is sahih. Umayr, freedman of Abbas, is Umayr bin Abdullah Hilali, freedman of Umm Fadl, wife of Abbas, though he is sometimes attributed in his clientship to Abdullah or Fadl, her two sons, as well.Askata, with a fatha on the hamza, is a four-letter verb. It is said, "The man spoke, then he fell silent" (sakata), without an alif. But when his speech was cut off so that he did not speak, it is said, "askata." It is also said that sakata means to deliberately remain silent, while askata means to become absorbed in thought, or from illness, or from fear.What is meant here is that he became absorbed in thought and so did not speak.