Musannaf Ibn Abi Shayba 3:1977

Ibn Fudayl narrated to us, from Isma'il, from al-Hasan, regarding a man who passes by a prostration (verse) during prayer: He said: It is not appropriate for him, when he passes by it, to omit it; rather, he should prostrate for it. And if he wishes, he may bow for it.