Conditions for the Acceptance of Actions
A brief explanation showing the two fundamental conditions necessary for any act of worship to be accepted by Allāh.
So whoever has his worship established from Allāh upon conformity to the Sunnah of His Prophet (ṣallallāhu ʿalayhi wa-sallam), and does not let it become mixed in with innovation, then let him rejoice in Allāh's acceptance of his obedience.
An action is not accepted by Allāh the Blessed and the Exalted, except if it contains two conditions:
Firstly: It should be done purely for the Face of Allāh the Mighty and Majestic.
Secondly: It should be righteous and it cannot be righteous, except if it is established from the sunnah, without opposing it. It has been confirmed by the researchers from the people of knowledge that every alleged act of worship that the Prophet (ṣallallāhu ʿalayhi wa-sallam) did not legislate by his statement, or which he did not perform in order to get closer to Allāh - is in opposition to the sunnah. So the sunnah consists of two parts, sunnatul fi'iliyyah (the sunnah of actions) and sunnatut tarkiyyah (the sunnah of abandonment). So whatever the Prophet (ṣallallāhu ʿalayhi wa-sallam) left off from acts of worship, then it is a sunnah to leave them off. Do you not see the likes of this in the aẓan (call to prayer) for the two 'eeds, and in burying the dead, even though a person may be engaged in the remembrance and glorification of Allāh the Mighty and Majestic. It is not permissible to draw near to Allāh by that.
Indeed, the Companions understood of the Prophet (ṣallallāhu ʿalayhi wa-sallam) understood this meaning, so they issued general warnings against innovations such as what is mentioned regarding this topic from Hudthayfah (raḍī Allāhu ʿʿʿanhu). He said: "Every act of worship that the Companions of the Messenger of Allāh did not perform, ten do not perform it." ʿAbdullāh Ibn Masʿūd (raḍī Allāhu ʿʿʿanhu) said: "Follow and do not invent, for indeed you have been sufficed. Stick to the old matters. 
So whoever has his worship established from Allāh upon conformity to the sunnah of His Prophet (ṣallallāhu ʿalayhi wa-sallam), and does not let it become mixed in with innovation, then let him rejoice in Allāh's acceptance of his obedience. Allāh will surely place him in Paradise. May Allāh make us from those who hear the statement and then obey in goodness.
Know that the innovation that you shall encounter is of two types:
Innovations which were extrapolated from a text, and their novelty is mentioned in the books of the people of knowledge, and this is a sign that it is traced back to them, and this type is abundant.
The other type is innovations that are not found in any text, rather the knowledge-based principles and foundations judge them to be innovations. So this is proof that they are void in origin.
So these innovations emanate from the following matters:
Firstly: Weak ḥadīths. It is not permissible to use them as evidence, or to attribute them to the Prophet (ṣallallāhu ʿalayhi wa-sallam). According to what I have explained in the introduction to 'Ṣifat Ṣalātin Nabī', the likes of this is not a permissible action with us, and this was the methodology of a group of the people of knowledge such as Ibn Taymīyyah.
Secondly: Fabricated ḥadīths, or those which there is no basis for. Their matter is well known to some of the fuqahaa` (legal jurists), yet they still base their rulings upon them. These are from the very essence of innovations and newly invented matters!
Thirdly: Reasoning, and approvals (istiḥsānaat) made by some of the legal jurists - especially the later ones from amongst them - not supported by any legislative proofs. Rather they are carried on as accepted matters of the Muslims, until they are made sunnahs to be followed! It is not hidden from one who has insight into his Religion, that this is not permissible to be followed, since nothing can be legislated except for that which is legislated by Allāh. So if an action is acceptable according to the approver - if he is a mujtahid - then Allāh will not punish him for it. As for the people who take that as legislation, or a sunnah, then no. So how can that be when some of these actions oppose the sunnah-related actions, as will follow if Allāh the Exalted wishes.
Fourthly: Customs or superstitions which are not from the Revelation, and are not testified to by the intellect, even though some of the ignorant people may act upon them, and take them as revelation. These cannot be supported by their authorities, even if some of them are from the callers to knowledge, or from those who have their appearance.
Then you should know that the danger of these innovations is not only in one matter, rather it is upon levels. Some of them are clear shirk (associating partners with Allāh) and disbelief, as you shall see, and some of them are less than that. However, it is obligatory upon us to know that the smallest innovation a man brings into the Religion is prohibited after its matter is clarified. So innovations are not - as some people think - at the level of dislike (makrooh) only. How can that be when the Messenger of Allāh (ṣallallāhu ʿalayhi wa-sallam) has said: "Every innovation is a misguidance, and every misguidance is in the Fire."?  That means, the one who does it is in the Fire.
Indeed, Imām al-Shāṭibī has confirmed this with the best of explanations in his book, 'al-I'itisaam'. Due to this, the matter of innovation is a great danger. Most of the people are ignorant about it, except for a group from the people of knowledge. So enough for you as a proof regarding the danger of innovation is the statement of the Messenger of Allāh: "Verily Allāh veils the repentance of every person of innovation, until he leaves his innovation." This is related by Ṭabarānī, and by Diyaa`ul Maqdisee in 'al-Aḥādīthul Mukhtaarah', and other than them with an authentic chain of narrators, and al-Mundthiree declared it good. (ḥasan) 
So I finish with these great words of advice to the reader from a great scholar from the early scholars of the Muslims. He was Shaykh Ḥasan Ibn ʿAlī al-Barbahārī, from the companions of the companions of Imām Aḥmad, he died in the year 329H. He said:
"So beware of small innovations, because they grow until they are large. Such was the case with every innovation invented into this Ummah. At first it was small, resembling the truth, so some were deceived by that and entered into it. Then it was not possible for them to leave from it, so it grew, and the Religion was split into religions due to it. So look - may Allāh have mercy upon you - into the statements of everyone you hear from, in you age particularly. So do not rush into, or enter into anything until you ask and see: 'Did anyone from the Companions of the Messenger of Allāh (ṣallallāhu ʿalayhi wa-sallam), or anyone from amongst the scholars talk about it?' So if you find a narration from them, then hold fast to it. Do not exceed it by anything, and do not give anything precedence over it, so as to fall into the Fire.
So know - may Allāh have mercy upon you - that a servant's Islām is not complete until he becomes and obedient, truthful Muslim. So whoever alleges that something remains from the matter of Islām, not completed by the Companions of the Messenger of Allāh (ṣallallāhu ʿalayhi wa-sallam), then he has indeed lied upon them, and has caused a schism by doing this, and he has lied upon them. So he is an innovator, misguided and misguiding, innovating into Islām what is not in it. 
May Allāh have mercy upon Imām Mālik since he said:
"The latter part of this ummah will not be rectified, except by that which rectified its first part. So whatever was not part of the Religion in those days, cannot be part of the Religion today. 
May Allāh have mercy upon our Prophet (ṣallallāhu ʿalayhi wa-sallam) who said:
"I have not left anything that will bring you close to Allāh, except that I have commanded you with it, and I have not left anything that will distance you from Allāh and bring you close to the Fire, except that I have forbidden you from it. 
The Praise is due to Allāh, by whose favour righteous actions are perfected.
 This is a translation of (p. 100-105) of the book, 'Hujjatun Nabī' by shaykh Muḥammad Nāṣir al Dīn al-Albānī.
 Translators Note: Reported authentically in al-Dārimī (no.211) at-Ṭabarānī in al-Kabīr (no. 8870), al-Bayḥaqī (no. 204), Ibn Wadaah in Bidʿah wa-al-Naḥī ʿAnhā p. 10, and also from Qatādah on p.11. Also related by Abī Khaythamah in al-'Ilm (no. 54). Shaykh al-Albānī has authenticated the narration in Bidʿah wa-al-Naḥī ʿAnhā.
 Translators Note: See: Ṣaḥīḥ Muslim (3/11), Aḥmad (3/381), Nisāʿī (1/234), al-Bayḥaqī (3/214). A full checking of this ḥadīth can be found in the book, 'Khutbatul Haajah' by shaykh Muḥammad Nāṣir al Dīn al-Albānī.
 Translators Note: See Silsilah al-Aḥādīth al-Ṣaḥīḥah (no. 1620).
 Related in Tabaqaatul Hanaabilah (2/18-19), of Ibn Abī Ya'ʿalá.
 Translators Note: Related in ash-Shifaa` of Qaadee `Iyyaadh, (2/676).
 Translators Note: Related in the Sunan of Imām al-Shāfiʿī (1/14), and by al-Bayḥaqī (7/76), and by al-Khaṭīb in al-Faqīḥ wal-Mutafaqqih (1/93).