Musannaf Ibn Abi Shayba 3:1872

Abu Usama narrated to us, from Ubaydullah, from Nafi’, from Ibn Umar, who said: He used to prostrate during [the recitation of] *An-Najm* and *Iqra’ Bismi Rabbika* [Surah Al-Alaq], unless he was reciting them during a prescribed prayer; for in that case, he would not prostrate during them, but would instead bow.