Is learning the fiqh of sales and financial transactions an individual obligation (fardh 'ayn) upon everyone who engages in buying and selling, such as pharmacists and pharmaceutical company representatives?

Seeking knowledge is an obligation upon every Muslim, and it is divided into a communal obligation (fard kifaya) and an individual obligation (fard ayn). That without which an obligation cannot be fulfilled is itself obligatory, such as learning the basic rules of worship and the rules of transactions for those who engage in them, in order to avoid the unlawful and dubious matters. It was reported from the Companions (may Allah be pleased with them) that they emphasized to merchants the necessity of understanding the rules of trade, and that whoever trades before understanding them will fall into usury.

A Muslim must know a set of rulings about which ignorance is not excused, such as monotheism, the pillars of Islam, and the prohibition of adultery, usury, and injustice. He must also ask about the unusual occurrences he encounters in his daily life.

Therefore, merchants are advised to read concise books on the jurisprudence of transactions.