Sahih al-Bukhari 4162
Narrated Sa`id bin Al-Musaiyab:
That his father said, "I saw the Tree (of the Ar-Ridwan Pledge of allegiance and when I returned to it 
later, I was not able to recognize it. (The sub--narrator MahmiJd said, Al-Musaiyab said, 'Then; forgot 
it (i.e., the Tree).)"
حَدَّثَنِي مُحَمَّدُ بْنُ رَافِعٍ، حَدَّثَنَا شَبَابَةُ بْنُ سَوَّارٍ أَبُو عَمْرٍو الْفَزَارِيُّ، حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ أَبِيهِ، قَالَ لَقَدْ رَأَيْتُ الشَّجَرَةَ، ثُمَّ أَتَيْتُهَا بَعْدُ فَلَمْ أَعْرِفْهَا‏.‏ قَالَ مَحْمُودٌ ثُمَّ أُنْسِيتُهَا بَعْدُ‏.‏