What are the foundations of Islam upon which the Companions, the Taabi‘is and the Muslim scholars agree?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Here are some of the numerous fundamentals of Islam, upon which the Companions and leading Muslim scholars agreed:

1- Testifying that there is none worthy of worship except Allaah The Almighty.

2- Affirming the oneness of Lordship of Allaah The Exalted for there is no Creator, Provider, Arranger of affairs and Owner of the creation except Him.

3- Believing in the Attributes of Allaah The Almighty that are mentioned in the Quran and authentic Hadeeths (narrations) of the Prophet without distorting their wordings or meanings, nor denying, nor asking how, nor drawing resemblance between Allaah The Almighty and any of His creation.

4- Testifying that Muhammad, sallallaahu ‘alayhi wa sallam, is the Messenger of Allaah and believing that his words are truthful, and avoiding what he prohibited.

5- Worshipping Allaah The Almighty in accordance with the Sharee‘ah (Islamic law) that the Prophet, sallallaahu ‘alayhi wa sallam, came with.

6- Holding the Prophet, sallallaahu ‘alayhi wa sallam, in high esteem and loving him more than one's self, property, children and all humankind.

7- Performing prayers.

8- Paying Zakah (obligatory charity).

9- Performing pilgrimage.

10- Fasting the month of Ramadan.

11- Believing in angels.

12- Believing in the Divinely-revealed Books, in general, and particularly in those that were mentioned in the Quran.

13- Believing in the Messengers of Allaah in general, and particularly in those who were mentioned in the Quran and the Sunnah. 

14- Believing in the Last Day and in everything that will occur in it, like the Siraat (Bridge over Hell), the Scale, the Hawdh (Basin), intercession, Paradise, Hell and seeing Allaah The Almighty. 

15- Believing in Fate and divine decree.

16- Pledging allegiance to the allies of Allaah The Almighty and declaring one’s enmity towards the enemies of Allaah The Almighty.

17- Being content with Allaah The Almighty as the only Lord, with Islam as the only accepted religion and with Muhammad, sallallaahu ‘alayhi wa sallam, as the Prophet and Messenger of Allaah.

18- Loving and hating for the sake of Allaah The Almighty.

19- Loving, defending and following the Companions of the Prophet, sallallaahu ‘alayhi wa sallam.

20- Disbelieving in anything that is worshipped other than Allaah The Almighty.

21- Disavowal of the disbelievers and harboring enmity towards disbelief.

22- Believing that Islam has been perfected beyond any human addition  and that every religious innovation leads to error.

23- Believing that the Prophet, sallallaahu ‘alayhi wa sallam, is the last prophet and that no prophets will come after him.

24- Believing in the entire contents of the Quran and the Sunnah.

25- Acknowledging what has been prohibited by Allaah The Almighty as being unlawful and what has been permitted by Him to be lawful.

26- Believing that judgment belongs only to Allaah The Almighty, as mentioned in the verse (what means): {Legislation is not but for Allaah. He has commanded that you worship not except Him.} [Quran 12:40] 

Allaah Knows best.