The Messenger of Allaah explained to the people -completely and clearly-what their Lord had revealed for them; both the detailed matters and the important ones, the apparent matters and the hidden ones, to such an extent that he taught them what they needed to know with respect to matters of eating, drinking, marriage, clothing and housing. So he taught them the ettiquettes of eating, drinking and relieving one's self; the ettiquettes of marriage; the ettiquettes of clothing and of entering and leaving the house - just as he taught them what they needed to know with regard to the worship of Allaah -The Mighty and Majestic-such as purification, Prayer, Zakaah, fasting, Pilgrimage and other than this.
He taught them what they needed to know with regard to the social behaviour with the people, such as kindness to parents, keeping ties of kinship, good companionship with friends and neighbours and other than this.He taught them how to conduct themselves in matters of buying and selling, pawning, leaving deposits, leasing, renting, giving and receiving donations, and other such matter, to such an extent that Abu Dharr(rta) said: "Indeed the Messenger of Allaah passed away and there is not a bird flapping its wings in the sky, except that he mentioned to us some knowledge about it" (2)
Foundations of the Deen
Salmaan al-Farsee (rta) narrated that it was said to him:Your Prophet has taught you everything, even how to relieve yourselves?So he said to them:"Yes indeed! And he has prohibited us from facing the qiblah (direction of prayer) whilst relieving ourselves..."(3) Along with this, he also taught them the foundation of all these acts of worship, manners and social interactions.
This foundation being what the worshippers hold as 'aqeedah (belief) concerning Allaah-the deity who is worshipped and who alone deservs to be worshippped -regarding His Dhaat (Essence), His Names, His Attributes and His Actions, and what follows from this regard to His Universal Laws and His prescribed Laws, which is based upon His ultimate Wisdom and utmost mercy.The Companions learnt all this from the Prophet, clearly and without any ambiguity, and all this was built upon the complete "Tawheed" of Allaah (to single out Allaah alone for worship), having as its foundations two great pillars: Affirmation and Negation.
As for affirmation: It is affirming what is due to Allaah-the Most High-from the rights of His Lordship, worship, and His names, attributes and actions.
As for negation: Then it is negating any partners to Allaah-the Most High-in all that is due to Him.
The People of Sunnah
Those who followed in goodness (ie in aqeedah and manhaj) from those who reached the period of the companions , or those who came after them from the Imaams of guidance-who deserved the Pleasure of Allaah - remained upon this path, as Allaah-the Most High-said:
"The first to embrace Islaam from the Muhaajireen(those who migrated from Makkah to al-Madeenah) and the Ansaar(those who lived in al-Madeenah and aided them after migration) and those who follow them in goodness(correct aqeedah and manhaj).Allaah is well pleased with them, as they are well pleased with Him.He has prepared for them Gardens beneath which rivers flow, to dwell therein forever.This is the suporeme achievement"(4)
Then they were followed by those who came later, being blind to the truth, or pretending to be blind to the truth.So they went astray and led others astray either due to inabilities or shortcomings, or due to enmity and oppression. They innovated in the Deen of Allaah -the Most High - that which did not belong to it, in matters of aqeedah (beliefs), ibaadah (acts of worship) and sulook (manners).They did this by altering the texts of the Book and the Sunnah; and of it was possible, they rejected them entirely!
Brief History of the Innovated Sects
Shaykh ul-Islaam Ibn Taymiyyah ( d.728H) said: "And know that most of the innovations connected to 'uloom(sciences) and acts of worship occured in this Ummah at the end of the period of the Rightly guided Khaleefahs; just asa the Prophet informed, when he said: "Those of you who live long after me will see a great deal of differences. So Hold fast to my Sunnah and the Sunnah of the Rightly Guided Khaleefahs after me"...So when the period of the Rightly Guided Khaleefahs had passed and the rule of kingship appeared, deficiencies appeared in the leaders, and therefore deficiency spread also to the people of knowledge and Deen.So during the end of the rule of 'Alee (rta) - the innovation of the Khwaarij (5) and Raafidah (6) appeared; this being connected to the issue of leadership and khilaafah, and what was connected to this from actions and Shareeah rulings.