It is narrated from Sayyiduna Miswar bin Yazid (may Allah be pleased with him); he said: I heard the Messenger of Allah (peace and blessings be upon him) reciting in the prayer, and he (peace and blessings be upon him) left out part of a verse which he did not recite. A man said: "O Messenger of Allah, it was such and such a verse." He (peace and blessings be upon him) said: "Why did you not remind me of it?" He said: "I thought that it had been abrogated."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17170