To the army officers when he was elected as the caliph
Nahj al-Balāgha|Volume 1|Book 2|Chapter 79
ومن كتاب له (عليه السلام) لما استخلف إلى أمراء الأجناد
To the army officers when Amīr al-mu’minīn became Caliph.
أَمَّا بَعْدُ، فإِنَّمَا أَهْلَكَ مَنْ كَانَ قَبْلَكُمْ أَنَّهُمْ مَنَعُوا النَّاسَ الْحَقَّ فَاشْتَرَوْهُ، وَأَخَذُوهُمْ بِالْبَاطِلِ فَاقْتَدَوْهُ.
Now, what ruined those before you was that they denied people their rights and then they had to purchase them (by bribes), and they led the people to wrong and they followed it.