Musannaf Ibn Abi Shayba 3:2017

Mu'adh ibn Mu'adh narrated to us, he said: 'Ali ibn Suwayd ibn Manjuf narrated to us, he said: Abu Rafi' informed us, he said: 'Umar led us in the final 'Isha' prayer, and he recited in one of the two rak'ahs: "When the sky has split asunder" (Idha al-sama'u inshaqqat), then he prostrated, and we prostrated with him.