Musannaf Ibn Abi Shayba 3:1239

Mu'adh ibn Mu'adh narrated to us, from Ali ibn Suwayd ibn Manjuf, he said: Abu Rafi' narrated to us, he said: I prayed the Isha prayer with Umar, and he recited: "When the sky has split [Idha al-sama'u inshaqqat]."