While the Prophet was alive, the Companions had consulted to him personally for the solution of every religious matter and to the Qur'an and Sunnah after his death. On the issues that they could not find information in the two sources mentioned, they have made judgments by making ijtihad. Those who were not at the level to make ijtihad obtained information by consulting to people who were experts in religious matters. The Muslims who came after them continued to follow the same path. Later on, fatwa books were prepared and these works began to be used in the field of qada as well as fatwa. Although the proposal for codification of Islamic law was made by Ibn Mukaffa' (d. 142/759) at a very early period, this proposal was not realized and the act of codification started too late. So much so that the Islamic world has lagged behind the West in legalizationThe codification activities that started in the modern western world after the French Revolution in the nineteenth century also affected the Islamic world, and as a result, the codification activities began to appear in the Islamic world too. These activities, initiated by the Ottoman State, pioneered the codification activity in the Islamic world, and then codification activities continued in other Islamic countries. Laws prepared by the Ottoman State, such as al-Majalla al Ahkam al Adliyyah (The Ottoman Courts Manual) and the Family Law Decree continued to be in force in some other Islamic countries a long time after they were declared abolished in Republic of Turkey. In addition, they affected directly or indirectly the law of Islamic countries such as Afghanistan that were never under Ottoman State’s rule. In this article, the effects of Ottoman law on Afghan law will be discussed in the context of criminal law, family law and law of obligations.