Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) said:
With regard to joining modern parties, this should not be done. Everyone should adhere to the Book of Allaah and the Sunnah of His Messenger, and cooperate in that sincerely. Thus they will be part of the “party of Allaah” of which Allaah says at the end of Soorat al-Mujaadilah (interpretation of the meaning):“Verily, it is the party of Allaah that will be the successful” [al-Mujaadilah 58:22], after mentioning their great attributes in the verse (interpretation of the meaning): “You (O Muhammad (peace and blessings of Allaah be upon him)) will not find any people who believe in Allaah and the Last Day, making friendship with those who oppose Allaah and His Messenger…”
Among their great attributes are those which Allah mentions in Soorat al-Dhaariyaat, where He says (interpretation of the meaning):
“Verily, the Muttaqoon (the pious. See V.2:2) will be in the midst of Gardens and Springs (in the Paradise),
16. Taking joy in the things which their Lord has given them. Verily, they were before this Muhsinoon (good‑doers. See V.2:112).
17. They used to sleep but little by night [invoking their Lord (Allaah) and praying, with fear and hope].
18. And in the hours before dawn, they were (found) asking (Allaah) for forgiveness.
19. And in their properties there was the right of the Saa’il (the beggar who asked) and the Mahroom (the poor who does not ask others)”
These are the attributes of the “party of Allaah”, who do not follow anything but the Book of Allaah and the Sunnah; they promote that and follow the path of the early generation of this ummah, the Sahaabah (may Allaah be pleased with them) and those who followed them in truth.
They sincerely advise and call upon all parties and groups to adhere to the Qur’aan and Sunnah and to examine anything that differs from them; whatever is in accordance with both or one of them (the Qur’aan and Sunnah) is acceptable and true, and whatever goes against them must be shunned.
In that regard there is no difference between the Muslim Brotherhood (al-Ikhwaan al-Muslimeen), Ansaar al-Sunnah, al-Jama’iyyah al-Shar’iyyah, Jamaa’at al-Tableegh and other groups and parties that claim to be Islamic. Thus they have a shared purpose and aim and become one party which follows the path of Ahl al-Sunnah wa’l-Jamaa’ah, who are the party of Allaah and the supporters and promoters of His religion.
It is not permissible to follow blindly any group or party in matters in which it goes against sharee’ah.
Majmoo’ Fataawa al-Shaykh Ibn Baaz (7/177, 178).