عَنْ أُبَيِّ بْنِ كَعْبٍ رَضِيَ اللَّهُ عَنْهُ قَالَ صَلَّى بِنَا النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ الْفَجْرَ وَتَرَكَ آيَةً فَجَاءَ أُبَيٌّ وَقَدْ فَاتَهُ بَعْضُ الصَّلَاةِ فَلَمَّا انْصَرَفَ قَالَ يَا رَسُولَ اللَّهِ نُسِخَتْ هَذِهِ الْآيَةُ أَوْ أُنْسِيتَهَا قَالَ لَا بَلْ أُنْسِيتُهَا
It is narrated from Sayyiduna Ubayy ibn Ka'b (may Allah be pleased with him), he says: The Noble Prophet (peace and blessings be upon him) led us in the Fajr prayer and while reciting, he left out a verse. When I arrived, I had missed a part of the prayer. In any case, when the Prophet (peace and blessings be upon him) finished, I said: O Messenger of Allah! Has such-and-such verse been abrogated or did you forget it? The Prophet (peace and blessings be upon him) replied: No, rather I forgot it.