Hadith: If Allah wills to do good to a ruler, He appoints for him a truthful adviser, who will remind him if he forgets and help him if he remembers. And if Allah wills otherwise for him, He appoints for him a bad adviser who will not remind him if he forgets, nor will he help him if he remembers.

عن عائشة رضي الله عنها مرفوعًا: «إِذَا أَرَادَ اللهُ بِالأمِيرِ خَيرًا، جَعَلَ لَهُ وَزِيرَ صِدقٍ، إِنْ نَسِيَ ذَكَّرَهُ، وَإِنْ ذَكَرَ أَعَانَهُ، وَإِذَا أَرَادَ بِهِ غَيرَ ذَلِكَ جَعَلَ لَهُ وَزِيرَ سُوءٍ، إِنْ نَسِيَ لَمْ يُذَكِّرهُ، وَإِنْ ذَكَرَ لَمْ يُعِنْهُ».
[صحيح] - [رواه أبو داود]

‘Ā’ishah (may Allah be pleased with her) reported that the Prophet (may Allah's peace and blessings be upon him) said: "If Allah wills to do good to a ruler, He appoints for him a truthful adviser, who will remind him if he forgets and help him if he remembers. And if Allah wills otherwise for him, He appoints for him a bad adviser who will not remind him if he forgets, nor will he help him if he remembers."
[Authentic hadith] - [Narrated by Abu Daoud]

Explanation

The Messenger of Allah (may Allah's peace and blessings be upon him) said: "If Allah wills to do good to a ruler." This goodness of granting an honest adviser was interpreted as the good of both abodes; this life and the Hereafter. It was also interpreted to be Paradise. His statement: "He appoints for him a truthful adviser" means truthful in his words and deeds, both inwardly and outwardly. He described him as being truthful because that is the basis of good companionship. So, if this ruler forgets something that he needs —given that forgetfulness is part of human nature— or if he is misled in a religious matter or a verdict against an oppressed person or in something related to the welfare of his subjects, then this truthful adviser will remind him and guide him to a sound judgment. Also, if this ruler knows the sound judgment, his truthful adviser will support him with his words and deeds. His statement: "If Allah wills otherwise for him" means other than good. His statement: "He appoints for him a bad adviser who will not remind him if he forgets, nor will he help him if he remembers" means that He will grant him an evil adviser who will be evil in his words and deeds, the opposite of the first case. If the ruler forgets or is misled, he will not assist him or guide him to what is right because he lacks the light in the heart which would allow him to help the ruler. If the ruler knows what to do, he will not assist him; rather, he will discourage him from doing the right thing due to his evil nature and bad intentions.