Sahih Bukhari Volume 2, Book 11, Hadith 928

حَدَّثَنَا إِسْمَاعِيلُ بْنُ أَبَانَ، قَالَ حَدَّثَنَا ابْنُ الْغَسِيلِ، قَالَ حَدَّثَنَا عِكْرِمَةُ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ صَعِدَ النَّبِيُّ صلى الله عليه وسلم الْمِنْبَرَ وَكَانَ آخِرَ مَجْلِسٍ جَلَسَهُ مُتَعَطِّفًا مِلْحَفَةً عَلَى مَنْكِبَيْهِ، قَدْ عَصَبَ رَأْسَهُ بِعِصَابَةٍ دَسِمَةٍ، فَحَمِدَ اللَّهَ وَأَثْنَى عَلَيْهِ ثُمَّ قَالَ ‏"‏ أَيُّهَا النَّاسُ إِلَىَّ ‏"‏‏.‏ فَثَابُوا إِلَيْهِ ثُمَّ قَالَ ‏"‏ أَمَّا بَعْدُ، فَإِنَّ هَذَا الْحَىَّ مِنَ الأَنْصَارِ يَقِلُّونَ، وَيَكْثُرُ النَّاسُ، فَمَنْ وَلِيَ شَيْئًا مِنْ أُمَّةِ مُحَمَّدٍ صلى الله عليه وسلم فَاسْتَطَاعَ أَنْ يَضُرَّ فِيهِ أَحَدًا أَوْ يَنْفَعَ فِيهِ أَحَدًا، فَلْيَقْبَلْ مِنْ مُحْسِنِهِمْ، وَيَتَجَاوَزْ عَنْ مُسِيِّهِمْ ‏"‏‏

Narrated By Ibn Abbas : Once the Prophet ascended the pulpit and it was the last gathering in which he took part. He was covering his shoulder with a big cloak and binding his head with an oily bandage. He glorified and praised Allah and said, "O people! Come to me." So the people came and gathered around him and he then said, "Amma ba'du." "From now onward the Ansar will decrease and other people will increase. So anybody who becomes a ruler of the followers of Muhammad and has the power to harm or benefit people then he should accept the good from the benevolent amongst them (Ansar) and overlook the faults of their wrong-doers."