Fiqh linguistically means understanding as in His  saying

That is, we do not understand. According to the definition of the legists, fiqh is designated as the knowledge of a body of subsidiary (furu’iyya) Sharī’ah rules acquired through study and eduction (istidlal). Knowledge of the Sharī’ah rules (ahkām shar’iah) began the day these Sharī’ah rules came to exist and that was after the migration (hijra) from Makkah to Madina. This is because the Messenger of Allah  was sent and he stayed in Makkah for thirteen years then he resided in Madina for about ten years and the Qur’ān used to be revealed throughout this period, though the verses of ahkām were revealed in Madina. In this period the Qur’ān used to be revealed and the Messenger  would talk about the ahkām relating to whatever they included in terms of events and relating to the solution for whatever problems that arose.

The portion that was revealed in Makkah approximates to about two thirds of the Qur’ān and they are designated as the Makkan verses (makkiyy). In their totality they barely deal with a single hukm, rather they are confined to explaining the fundamentals of the deen and calling people to them, such as the belief in Allah  and His Messenger , the Day of Judgement, the command to perform Salah, characterisation by moral attributes such as honesty, trust, and forbidding evil actions such as fornication, murder, burying girls alive, deficiency in the measure and scales etc. The second portion that was revealed in Madina is close to a third of the Qur’ān and they are designated as the Madinan verses (madaniyy). They are verses of mu’amalat (transactions) such as selling, renting and usury and from the hudud, such as the hadd of zina (fornication) and stealing, from the jinayat (capital punishments) such as killing the one who killed someone intentionally or punishment of highway robbers and from the bayyinat (testimonial evidences) such as the testimony of zina and the rest of the testimonies, as well the remaining rules concerning the worships (‘ibadat) such as fasting, zakah, hajj and jihad were revealed. From this it becomes clear that even though rules of prayer were revealed in Makkah they do not form a body of rules but knowledge of a type of rule. As for what was revealed in Madina, they consisted of all the ahkām, which is why knowledge of such rules is considered fiqh. Therefore, it is more accurate for us to say that fiqh began in Madina and since fiqh constitutes practical rules, they have been revealed to treat incidents that have taken place. The verses of ahkām more often than not were in connection to the events that had taken place, so the disputants would refer judgement to the Messenger of Allah  and he  would judge between them according to the rules that Allah  had revealed to him  or on the occasion of problems requiring solutions an ayah or ayaats stating the hukm would be revealed. This is what it means for the Qur’ān to be revealed gradually (munajjaman). Therefore, the legislative aspect used to be quite evident in the revelation of the Qur’ān. The ayaats did not treat assumptions that may happen; rather, they treated issues that actually took place and problems that actually take place between people. The Qur’ān continued to be revealed until the year in which the Messenger of Allah  left for the Sublime Companion (al-rafiq al-a’la). Allah  perfected and completed the deen and He  revealed to him  the last ayah which is His  saying in Sura al-Baqara:

With it the ahkām were completed in their capacity as ahkām. The Qur’ān and the actions, sayings and consent of the Messenger  contain the rulings for all the types of actions that ensue from human beings; from the worships (‘ibadat) like prayer (salah) and zakat, from the morals such as honesty and trust, from the societal transactions (mu’amalat) such as murder and theft, from the testimonial evidences (bayyinat) such as the rules of testimonies and the rules of written documents and from the political affairs relating to the domestic policy such as the rules of the Khalifah and the rules of the judiciary, or relating to the foreign policy such as the rules of combatants and treaties. Due to the presence of the Sharī’ah rules jurispudence (fiqh) came into existence because fiqh is the knowledge of a body of Sharī’ah rules.