[Pooya/Ali Commentary 24:33] A Muslim cannot satisfy his natural cravings outside marriage. If he cannot afford to maintain a family he must wait for Allah's grace and keep himself chaste until Allah gives him sufficient means. In religion fasting has been recommended for such a person. Kitab refers to a written instrument which allows a slave to redeem himself on paying a certain amount. This document obliges the master to set his slave at liberty on receiving the agreed amount which the slave collects either by his labour or by receiving donations from others. See fiqh. Slavery is now obsolete. Islam made it possible to put an end to slavery by enacting laws which, step by step, gave freedom to slaves. See the commentary of al Baqarah: 177. To set a slave free was considered to be one of the most distinguishing qualities of a believer. The Holy Prophet came with the divine message of Islam in a world wholly governed by the institution of slavery. A worst form of slavery was the basis of all human activity, social, economic and political. In such a predominantly slave-based system of social order Islam began to liberate slaves. According to Imam Jafar bin Muhammad as Sadiq it is the duty of a true believer to forgo the agreed amount if the slave desires freedom. Although the Imams among the Ahl ul Bayt gave freedom to their slaves but it is a historic fact that most of them refused to leave the service of the Imams. Even today the free followers of these Imams feel proud to say that they are the slaves (followers) of the Imams of the Ahl ul Bayt. What is now called the "white slave traffic" was carried on by wicked people like Abdullah ibn Obay who hired six women slaves for prostitution. According to this verse no more despicable trade can be imagined, so it is emphatically condemned and prohibited.