Rabi'ah bin Abi Abd al-Rahman (may Allah have mercy on him) narrates from their scholars that those killed on the day of the Camel, the day of Siffin and the day of al-Harrah were not made heirs of one another; then on the day of Qudayd too, none of those who were killed was made an heir of his companion, except where it was known who had died first.
Imam Malik (may Allah have mercy on him) said: There is no disagreement among us on this matter, nor any doubt about it among any of the people of knowledge in our city. And our Imam Ahmad (may Allah have mercy on him) narrates from Iyas bin Abd al-Muzani that some of them are to be made heirs of others; but the view of the majority is more correct.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12258