shall be no fear, nor shall they grieve." It also affirms family life by legislating on matters of marriage, divorce, and inheritance. A number of practices, such as usury and gambling, are prohibited. The Quran is one of the fundamental sources of Islamic law (sharia). Some formal religious practices receive significant attention in the Quran including the formal prayers (salat) and fasting in the month of Ramadan. As for the manner in which the prayer is to be conducted, the Quran refers to prostration. The term for charity, zakat, literally means purification. Charity, according to the Quran, is a means of self-purification. Encouragement for the sciences The astrophysicist Nidhal Guessoum, while being highly critical of pseudo-scientific claims made about the Quran, has highlighted the encouragement for sciences that the Quran provides by developing "the concept of knowledge." He writes:The Qur'an draws attention to the danger of conjecturing without evidence (And follow not that of which you have not the (certain) knowledge of... 17:36) and in several different verses asks Muslims to require proofs (Say: Bring your proof if you are truthful 2:111), both in matters of theological belief and in natural science.Guessoum cites Ghaleb Hasan on the definition of "proof" according to the Quran being "clear and strong... convincing evidence or argument." Also, such a proof cannot rely on an argument from authority, citing verse 5:104. Lastly, both assertions and rejections require a proof, according to verse 4:174. Ismail al-Faruqi and Taha Jabir Alalwani are of the view that any reawakening of the Muslim civilization must start with the Quran; however, the biggest obstacle on this route is the "centuries old heritage of tafseer (exegesis) and other classical disciplines" which inhibit a "universal, epidemiological and systematic conception" of the Quran's message. The philosopher Muhammad Iqbal, considered the Quran's methodology and epistemology to be empirical and rational. There are around 750 verses in the Quran dealing with natural phenomena. In many of these verses the study of nature is "encouraged and highly recommended", and historical Islamic scientists like Al-Biruni and Al-Battani derived their inspiration from verses of the Quran. Mohammad Hashim Kamali has stated that "scientific observation, experimental knowledge and rationality" are the primary tools with which humanity can achieve the goals laid out for it in the Quran. Ziauddin Sardar built a case for Muslims having developed the foundations of modern science, by highlighting the repeated calls of the Quran