In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Shaikhul Islaam Ibn Taymiyyah [rahimahullaah] said:
A notification to the one in charge of the affairs of the Muslims-may Allaah guide him-that the *Raafidah are not fit to be in authority over the Muslims in anything. They are not suitable for service in their troops and armies. And that is because they are the severest in enmity and harm against the Muslims than the Tartar enemies. Likewise, they are enemies of the Muslim Rulers–their enmity is based on religion and religious enmity is more severe than enmity [based on] worldly affairs. And an enemy betrays, deceives and double-crosses.
*If the Raafidah manifest repentance to the Muslim rulers and freedom from Rafd [i.e. their evil beliefs of shirk, kufr etc], he [the Muslim ruler] should not believe them merely based on that; rather he should be cautious about their affair. He should split their group and make them take residence in different places in the country in which they will be [living] amongst Ahlus Sunnah. That is because if the affairs change and their state of affairs change, and thus they manifest the enmity in their souls, they will be known and exposed. They will not be able to aid one another in evil and corruption, as opposed to if they were [all] in specific places on their own, then indeed they will have strength and numbers, and will aid one another in evil. And neither will many of their plots be known nor what they are planning to carry out of evil.
*The Raafidah take shelter with the people of evil and corruption in general-those who plot against the servants [of Allaah], the [Muslim] lands and the [Muslim] rulers, such as the heretics- the Qaraamita, the Ismaa’eeliyyah, the Nusayriyyah and their ilk.
*Repelling the harm of the Raafidah from the Muslims and their lands is from the greatest [acts] of sincerity to Allaah; sincerity to the Messenger [i.e. adherence to his Sunnah, obeying his commandments and keeping away from what he has forbidden, and believing everything he has informed of]; sincerity to the Muslim leaders [i.e. obedience to the Muslim leaders in good, making du’aa for them and giving them good advice in private and not to rebel against them etc] and sincerity to the common people [i.e. loving for them what you love for yourself, advising them, commanding them good and forbidding them from evil, preventing them from what harms them and guiding them to what is of benefit to them in this life and the next etc].
Abridged and slightly paraphrased. See link: http://www.sahab.net/forums/index.php?showtopic=126341]