Pada era para Sahabat (sahabah), kaum Muslimin biasa mengeluarkan Ahkam Syar'iyyah dari Kitab dan Sunnah dengan usaha mereka sendiri. Para hakim, ketika menangani perselisihan di antara manusia, akan menyimpulkan sendiri hukum syar'i bagi setiap isu atau peristiwa yang mereka hadapi. Para penguasa, bermula dari Amirul Mukminin hingga para Wali dan selainnya, akan menyimpulkan sendiri Ahkam Syar'iyyah untuk menyelesaikan setiap masalah yang timbul semasa pemerintahan mereka. Abu Musa al-Ash'ari dan Shuraih (raa) adalah dua orang qadi yang menyimpulkan hukum-hukum (Ahkam) dan mengadili dengan ijtihad mereka sendiri. Mu'adh bin Jabal (r.a) adalah seorang gabenor (wali) pada zaman Nabi ﷺ dan biasa menyimpulkan hukum-hukum serta memutuskan di dalam wilayahnya dengan ijtihad beliau sendiri. Abu Bakr dan Umar (ra) kedua-duanya menyimpulkan hukum-hukum dengan sendiri semasa pemerintahan mereka, dan kedua-duanya memerintah rakyat dengan ijtihad yang masing-masing telah mereka simpulkan. Muawiyah dan Amr bin al-'Aas adalah dua orang gabenor yang menyimpulkan hukum-hukum bagi diri mereka sendiri dengan ijtihad mereka dan memerintah rakyat menurutnya di wilayah masing-masing. Walaupun para hakim dan gabenor melakukan ijtihad, Khalifah biasanya memilih hukum-hukum tertentu dan memerintahkan pelaksanaannya oleh rakyat, yang wajib melaksanakan hukum-hukum yang dipilih itu dan meninggalkan pendapat serta ijtihad mereka sendiri mengenainya. Ini kerana hukum syar'i menetapkan bahawa keputusan Imam wajib dilaksanakan secara terbuka dan secara tersembunyi. Contohnya ialah pilihan Abu Bakr bahawa lafaz talak tiga sekaligus dalam satu majlis hanya membentuk satu talak, dan pilihan beliau bahawa harta hendaklah dibahagikan sama rata di kalangan kaum Muslimin tanpa mengira masa mereka memeluk Islam atau apa-apa perkara lain. Kaum Muslimin mengikuti Abu Bakr dalam pilihan-pilihan ini, dan para hakim serta gabenor melaksanakannya. Apabila Umar memegang jawatan selepas beliau, beliau memilih pendapat yang berbeza dalam soalan-soalan yang sama. Dia mewajibkan orang ramai menerima dan melaksanakan pengucapan talak tiga sekaligus dalam satu majlis sebagai tiga talak, dan dia membahagikan dana secara berbeza mengikut masa orang-orang itu memeluk Islam dan mengikut keperluan. Kaum Muslimin mengikuti 'Umar dalam pengambilan keputusan ini, dan para hakim serta gabenor melaksanakannya. 'Umar juga membuat keputusan bahawa tanah yang diperoleh melalui peperangan ialah ghanimah yang dimiliki oleh Bait ul Mal (Perbendaharaan Negara), di mana pemilik asal tetap menguasai tanah tersebut dan tanah itu tidak diagihkan kepada tentera Muslim atau kaum Muslimin. Para gabenor dan hakim mengikutinya dalam keputusan ini dan melaksanakan hukum-hukum yang telah dipilihnya. Oleh itu, ijma' para Sahabat (ijma'a as-sahabah) menegaskan bahawa Imam mempunyai kuasa untuk memilih peraturan tertentu dan memerintahkan agar ia dilaksanakan, dan kaum Muslimin wajib mentaatinya, walaupun ijtihad mereka berbeza daripadanya. Antara kaedah syariah yang terkenal ialah:

During the era of the Companions (sahabah), the Muslims used to extract the AHkam shar’aiah from the Book and the Sunnah by themselves. The judges, when tackling the disputes among people, would deduce by themselves the hukm shar’ai for every issue or event that they were faced with. The rulers, starting with the Ameer al-Mu'mineen to the Wulat and others, would themselves deduce the AHkam shar’aiah to solve every problem that arose during their ruling. Abu-Musa al Ash'ari and ShuraiH (raa) were two judges (qadi) who deduced the rules (AHkam) and judged by their own ijtihad. Mu'adh ibn Jabal (r.a) was a governor (wali) at the time of the Prophet (saw) and used to deduce aHkam and ruled in his wilayah by his own ijtihad. Abu Bakr and Umar (ra) both deduced aHkam by themselves during their ruling and both ruled the people with the ijtihad each of them had deduced. Muawiya and Amr ibn al 'Aas were two governors who deduced aHkam for themselves by their own ijtihad and ruled people in accordance with it in their provinces. In spite of the ijtihad undertaken by the judges and governors, the Khaleefah used to adopt certain aHkam and to order their execution by the people who would be obliged themselves to implement the adopted rules and to leave their own opinion and ijtihad on those rules. This is because the hukm shar’ai states that the Imam's decree is to be executed openly and covertly. Examples of this is Abu Bakr's adoption that the pronouncement of divorce three times in one sitting constitutes only one divorce, and his adoption that funds should be equally distributed among Muslims irrespective of the time when they embraced Islam or any other matter. The Muslims followed Abu Bakr in these adoptions and the judges and governors executed them. When 'Umar came to office after him he adopted different opinions in the same questions. He obliged people to accept and execute the pronouncement of divorce three times in one sitting as three divorces, and he distributed the funds differently according to the time when the people had entered Islam and according to need. The Muslims followed 'Umar in these adoptions and the judges and governors executed them. 'Umar also made the adoption that land obtained in war was a ghanima owned by the Bait ul Mal (House of Funds), wherein the original owners would retain possession and not distribute the land to the Muslim soldiers or the Muslims. The governors and judges followed him in this adoption and enacted the aHkam he had adopted. Accordingly, the consensus of the Companions (ijma'a as-sahabah) confirms that the Imam has the authority to adopt certain rules and order that they be executed and the Muslims must obey him, even if their ijtihad differs from it. Among the well known shar’aiah principles are:

"Sultan berhak mengeluarkan keputusan sebanyak masalah-masalah yang benar-benar wujud";

"The Sultan has the right to adopt decrees as numerous as the actual problems";.

"Keputusan Imam menyelesaikan perselisihan"; dan.

"The Imam's decre e resolves the discord"; and.

"Perintah Imam dilaksanakan secara terbuka dan secara tersembunyi."

"The Imam's command is executed openly and covertly".

Selepas itu, para Khulafa' menerima pakai hukum-hukum yang tertentu. Harun ar-Rasyid, sebagai contoh, menerima pakai kitab Kitab al-Kharaj dalam urusan ekonomi, dan beliau mewajibkan semua rakyat melaksanakan hukum-hukum yang terkandung di dalamnya.

Henceforth, the Khulafa'a adopted specific AHkam. Haroon ar-Rasheed, for example, adopted the book Kitab al-Kharaj in the economic affairs, and he obliged all the people to execute the AHkam included within it.