Allah (swt) says in the Holy Qur’an:
وَالْمُطَلَّقَاتُ يَتَرَبَّصْنَ بِأَنْفُسِهِنَّ ثَلاثَةَ قُرُوءٍ
“Divorced women shall wait concerning themselves for three quru’“.
(al-Baqarah: 228 )
This ayah informs us about the time period of ‘iddah for a divorced woman. It is from the Qur’an so there is no doubt about it. So how can there be differences of opinion about something like this, when it is clearly found in the Qur’an? How can there be ikhtilaf (differences of opinion) about something which Allah (swt) has spoken about directly? The reason is because of the word “quru”” used in the ayah. Most translations translate it as the menstrual cycle of a woman, i.e her haid. So that’s it then, right? A divorced woman must wait for three haids and then her ‘iddah ends. Actually its not as cut and dried as that. This is because the word qur is a homonym: it has more than one meaning. The first meaning is the haid of a woman, which is usually how this word is translated, but it could also mean the tuhr (clean) period between two haids. Here the two meanings are the exact opposite of the other! So which of the two is meant? This is where madhahib come in. One Imam would regard “qur ” as being haid and another would see it as being tuhr. Even the Sahabah (ra) differed amongst themselves concerning this mas’alah. So if there are differences of opinion concerning ayat of the Qur’an, which are all qat’i (definitive), then how much more ikhtilaf must there not be about ahadith which are zanni (speculative), and which must first be declared authentic by a muhaddith? Each Imam had different criterion for accepting ahadith so naturally this, as well as other factors, led to them having different opinions. And different opinions = the formation of madhahib. The fact that even the Sahabah (ra) differed about the ayah mentioned above shows that such differences were not a later development, it was present right from the time of the demise of the Prophet (saw). The only difference is that in the time of the four Imams the laws of fiqh were codified, which was not done previously. When this was done, madhahib were formed.