Is supplication for the ruler a requirement of the pledge of allegiance?

Q: Is supplication for the ruler, may Allah preserve you, a requirement of the pledge of allegiance?

A: Among the requirements of the pledge of allegiance is giving sincere advice to the ruler. Part of this advice is supplicating for him for success, guidance, rectitude of intention and action, and the rectitude of his inner circle. This is because among the causes of a ruler’s rectitude and among the causes of Allah’s success for him is that he has a truthful minister who assists him in good, reminds him when he forgets, and supports him when he remembers. This is among the causes of Allah’s success for him.
Therefore, it is obligatory for the subjects, and specifically for the prominent figures among the subjects, to cooperate with the ruler in reform, in extinguishing evil and eradicating it, and in establishing good through kind words, good manners, and sound guidance from which good is hoped for rather than harm. Any action that results in more harm than benefit is not permissible. This is because the objective of all authorities is to realize the benefits prescribed by the Shari'ah and to ward off harms. Therefore, any action a person performs intending good, but which results in something worse than what he intended to remove, or which is blameworthy, is not permissible for him.
The Shaykh al-Islam Ibn Taymiyyah, may Allah have mercy on him, clarified this meaning completely in his book "Al-Hisbah." It should be consulted for the great benefit it contains.