Musannaf Ibn Abi Shayba 24:172

Ibn Fudayl narrated to us, from ‘Ata’ ibn al-Sa’ib, who said: More than one person informed me that a judge from the judges of the people of Syria came to ‘Umar and said: "O Commander of the Faithful, I saw a vision that terrified me." ‘Umar said: "And what did you see?" He said: "I saw the sun and the moon fighting, and the stars were with them, divided into two halves." ‘Umar said: "And with which of them were you?" He said: "I was with the moon against the sun." ‘Umar said: "‘And We have made the night and the day as two signs, so We erased the sign of the night and made the sign of the day visible’ (Quran 17:12). Depart, for by Allah, you shall never work for me in any capacity ever again." ‘Ata’ said: It reached me that he was killed alongside Mu’awiyah on the day of Siffin.