بِسۡمِ ٱللهِ ٱلرَّحۡمَـٰنِ ٱلرَّحِيمِ
Shaikhul Islaam Ibn Taymiyyah (rahimahullaah) said:
Indeed, there has been much confusion in this subject matter just as it is the case in the subject matter of halaal and haraam. Indeed a group of people make permissible some of the things which Allaah has declared impermissible and others declare impermissible some of those things which Allaah has made permissible. Likewise some people innovate acts of worship that have not been legislated by Allaah; rather He (The Most High) prohibited them.
The foundation of the religion of Islaam is that the permissible affairs are those that Allaah and His Messenger have made permissible, and the impermissible affairs are those that Allaah and His Messenger have made impermissible. It is not allowed (or befitting) for anyone to leave the straight path which Allaah sent His Messenger with. Allaah (The Most High) said:
وَأَنَّ هَـٰذَا صِرَٲطِى مُسۡتَقِيمً۬ا فَٱتَّبِعُوهُۖ وَلَا تَتَّبِعُواْ ٱلسُّبُلَ فَتَفَرَّقَ بِكُمۡ عَن سَبِيلِهِۦۚ ذَٲلِكُمۡ وَصَّٮٰكُم بِهِۦ لَعَلَّڪُمۡ تَتَّقُونَ
”And verily, this is my Straight Path, so follow it, and follow not (other) paths, for they will separate you away from His Path. This He has ordained for you that you may become pious’”[6:153]
Abdullaah Ibn Mas’ood (radiyallaahu-anhu) reported that the Prophet (sallal-laahu-alayhi-wasallam) drew a line for us and said: ”This is Allaah’s Straight Path.” Then he drew lines to its right and left and then said: ”These are other paths. Upon every one of them there is a devil calling towards it.” Then he recited: “وَأَنَّ هَـٰذَا صِرَٲطِى مُسۡتَقِيمً۬ا فَٱتَّبِعُوهُۖ وَلَا تَتَّبِعُواْ ٱلسُّبُلَ فَتَفَرَّقَ بِكُمۡ عَن سَبِيلِهِۦ ”Indeed this is My Straight Path, so follow it. And do not follow other paths; they will separate you from His Path.” [Hadeeth reported by Imaam Ahmad in Al-Musnad 4437]
Indeed Allaah has mentioned in Soorah Al-An’aam, Soorah Al-A’raaf and other them regarding the deeds the idol worshipers were rebuked for, when they made impermissible the things that Allaah (The Most High) have not declared impermissible, such as the Baahirah (i.e. a she-camel whose milk was spared for the idols and nobody was allowed to milk it) and the Saa’ibah (a she-camel let loose for free pasture for their false gods, e.g. idols, etc., and nothing was allowed to be carried on it). They (also) made permissible those (deeds) which Allaah made impermissible, such as the killing of their children, and they instituted a religion which Allaah did not allow. Allaah (The Most High) said:
أَمۡ لَهُمۡ شُرَڪَـٰٓؤُاْ شَرَعُواْ لَهُم مِّنَ ٱلدِّينِ مَا لَمۡ يَأۡذَنۢ بِهِ ٱللَّهُۚ
”Or have they partners with Allah (false gods), who have instituted for them a religion which Allah has not allowed.” [42:21]
And there were impermissible affairs which they established as acts of worship, such as shirk, and lewd behaviour, such as Tawaaf around the Kabah, whilst being naked.
To be continued In-Shaa-Allaah
[Source: Al-Ibaadaat Ash-Shar-iyyah Wal-Farq Baynahaa Wa Baynal Bid’ah (page 7-8). Abridged and partly paraphrased]