How did the scholars divide knowledge into an individual obligation and a collective obligation?

Question : Peace be upon you, Shaykh. How, Shaykh, did the scholars divide knowledge into two categories: obligatory knowledge and knowledge that is a collective obligation?

Answer : Yes, that is correct. The knowledge you need is an individual obligation (fard 'ayn), meaning your knowledge of the rulings of prayer. You will pray, so you must worship Allah with understanding. Knowledge may come from books or from observing people. Most people today pray by observing others, having not read the books. As for the collective obligation (fard kifayah), it is what you do not need personally, but the Muslim community (ummah) needs. This includes knowledge of the rulings of sales, leasing, pledges, endowments (waqf), and the like. If you are not a seller, a lessee, one who makes endowments, or the like, then it is not your individual obligation.