كتاب مناقب الأنصار
Read the English translation first, with the original Arabic directly underneath.
Narrated Ibn `Abbas:
Allah's Messenger (in his fatal illness) came out wrapped in a sheet covering his shoulders and his head was tied with an oily tape of cloth till he sat on the pulpit, and after praising and glorifying Allah, he said, "Then-after, O people! The people will go on increasing, but the Ansar will go on decreasing till they become just like salt in a meal. So whoever amongst you will be the ruler and have the power to harm or benefit others, should accept the good of the good-doers amongst them and excuse the wrongdoers amongst them."
أَمَّا بَعْدُ، أَيُّهَا النَّاسُ، فَإِنَّ النَّاسَ يَكْثُرُونَ وَتَقِلُّ الأَنْصَارُ، حَتَّى يَكُونُوا كَالْمِلْحِ فِي الطَّعَامِ، فَمَنْ وَلِيَ مِنْكُمْ أَمْرًا يَضُرُّ فِيهِ أَحَدًا أَوْ يَنْفَعُهُ، فَلْيَقْبَلْ مِنْ مُحْسِنِهِمْ، وَيَتَجَاوَزْ عَنْ مُسِيئِهِمْ