Explanation of Hadeeth Number 5
This hadeeth is a Great Principle from amongst the Principles of the Religion, and it is an example of the Perfect and Concise Speech of the Messenger sallAllaahu alayhi wa salaam, as in it is found a clear rejection of every innovation (bid'ah) and every innovator. And this hadeeth is also used as a proof of the invalidity of every contract prohibited by the Sharee'ah, and also by some of the scholars of Usool ul-Fiqh when they say that a prohibition implies the invalidity of that action.
And in the second narration which states that "He who does an act which we have not commanded, will have it rejected" there is a clear and unequivocal command to leave all things which are newly introduced into the religion, whether the person invents that action himself or whether he follows someone else who has preceeded him. For verily some of the obstinate innovators give as a proof for their innovation the fact that they themselves have not introduced the innovation, but rather they are following the action of someone else - and they use the first hadeeth above to show that they are then not blameworthy.
And this hadeeth should be acted upon meticulously in all our affairs, and it should be preserved and spread amongst the people and used as an evidence to show the invalidity of all innovations and evil actions, for verily it includes in its meaning all of that.
However, as for the Furoo' (branches) of knowledge which are established from the Usool (basic principles) and which do not depart from the Sunnah, then these are not referred to by this hadeeth. For example, the writing down of the Qur'aan as a Mus-haf by 'Uthmaan (radiAllaauh 'anhu), or the establishment of the various madhhabs in Fiqh (Schools of Jurisprudence), which are from the understanding of the Mujtahid scholars of Fiqh, those who built the matters of Furoo' upon the Usool (which are the statements of the Prophet sallAllaahu alayhi wa sallam). And also, from amongst the matters not included in this hadeeth is the writing of books on subjects such as Grammar, or Arithmetic, or the Laws of Inheritance, and other than that from the sciences that are built upon the statements and commands of the Messenger of Allaah sallAllaahu alayhi wa sallam.
That anything new introduced in the matter of worship, which has not already been given sanction from the Qur'aan and the Sunnah will not be accepted by Allaah.
That anything new incorporated into the Deen must be thrown away and rejected by the Muslims.http://www.islaam.net/main/display.php?id=134&category=24