Is Learning Fiqh of Financial Transactions Essential?
Question

Is learning the fiqh of buying and selling and financial transactions obligatory (fard ‘ayn – an individual obligation) for everyone who engages in buying and selling, such as a pharmacist and representatives of pharmaceutical companies?
Praise be to Allah.If the Muslim understands that the purpose and aim of his being created in this world is to adhere to the laws of Allah, and to worship Allah by doing so, then he will also understand that it is essential for him to learn the rulings of Allah’s laws and learn what his duties are. That is because what is needed in order to do what is obligatory is also obligatory.  
It says in the hadith that the Prophet (peace and blessings of Allah be upon him) said: “Seeking knowledge is obligatory for every Muslim .” (Narrated by Ibn Majah (224) and classed as hasan because of its many isnads and corroborating reports by al-Mazzi, al-Zarkashi, al-Suyuti, al-Sakhaawi, al-Dhahabi, al-Manawi, and al-Zarqani. It is also in Sahih Ibn Majah by al-Albani.) 
The scholars have stated that the meaning of this hadith is sahih. 
Ibn ‘Abd al-Barr (may Allah have mercy on him) said:  
“But its meaning is sahih in their opinion, even though they differed somewhat concerning it." (Jami’ Bayan al-‘Ilm  1/53)
Al-Nawawi said something similar in al-Mathurat (p. 287), as did Ibn al-Qayyim in Miftah Dar al-Sa’adah (1/480). 
Ibn ‘Abd al-Barr also said: 
“The scholars are unanimously agreed that acquiring some types of knowledge is an individual obligation, which each person must learn for himself, and acquiring other types of knowledge is a communal obligation – if some people acquire it then the obligation of others is waived." (Jami’ Bayan al-‘Ilm wa Fadlihi  1/56) 
The scholars (may Allah have mercy on them) have described the knowledge which must be learned on an individual basis, and they have spoken of the amount of knowledge which each Muslim must acquire. They said that this includes learning the rulings on selling for those who engage in trade, so that they will not do anything haram or fall into riba (usury) without realizing. There are reports from the Companions (may Allah be pleased with them) which support that. 
‘Umar ibn al-Khattab (may Allah be pleased with him) said: “No one should sell in our marketplace except those who have knowledge of Islam.” (Narrated by al-Tirmidhi, 487, who said: it is hasan gharib. It was also classed as hasan by al-Albani in Sahih al-Tirmidhi.) 
‘Ali ibn Abi Talib (may Allah be pleased with him) said: “Whoever engages in trade before learning will fall into riba, then fall into riba.” (Mughni al-Muhtaj 2/22) 
Ibn ‘Abd al-Barr said: 
“What all people must learn is that which they cannot afford to be ignorant of such as bearing witness verbally and believing in the heart that Allah is One and has no partner or associate, and that His names and attributes are eternal; He has no beginning and no end, and He has risen over the Throne. 
He should bear witness that Muhammad is His slave and Messenger, and that all people will be resurrected after death to be rewarded or punished for their deeds, and that the Quran is the Word of Allah, and that what is in it is true.  
He should affirm that the five daily prayers are obligatory, and he must know what is essential for the performance of the prayer, such as purification and other rulings. 
He should affirm that fasting Ramadan is obligatory, and he must know what invalidates the fast and what is essential for the completion of the fast. 
If he has enough wealth and is physically able to perform Hajj, he must know what zakah is due on, and when it becomes due, and on how much it is due. He must perform Hajj once in his life if he has the means.
And there are things that he must know in general and he has no excuse for not knowing: such as the fact that zina and riba are forbidden, as are alcohol, pork, eating dead meat and all impure things, embezzling, bearing false witness, consuming people’s wealth unlawfully, all kinds of wrongdoing and oppression, marrying one’s mother or sister or any of those who are mentioned with them, and killing a believer unlawfully. 
And he must know all other things that are mentioned in the Book and that the ummah is agreed upon." (Jami’ Bayan al-‘Ilm  1/57) 
It says in al-Mawsu’ah al-Fiqhiyyah (30/293): 
“Ibn ‘Abidin said, quoting from al-‘Allami: 
It is obligatory for every accountable person, male or female , after learning about religion and guidance, to learn about wudu, ghusl, prayer, fasting, zakah for those who have the nisab (minimum threshold of wealth) and Hajj for those for whom it is obligatory. 
Merchants must also learn the rulings on trade, so that they can avoid doubtful and makruh things in their transactions ; the same applies to those who follow professions. 
Everyone who works with something must learn the rulings concerning it so that he can avoid what is haram. 
Al-Nawawi said: "As for selling, marriage and the like – which are not obligatory per se – it is haram to engage in them until one has learned their conditions.”
Al-Ghazali (may Allah have mercy on him) said: 
“If a Muslim is a merchant and riba is widespread in the land, he must learn about the prohibition on riba. This is knowledge which is an individual obligation, i.e., knowledge of how to do what is required." (Ihya ‘Ulum al-Din  1/33) 
‘Ali ibn al-Hasan ibn Shaqiq said to Ibn al-Mubarak: 
“What can the believer do with knowledge except seeking it? What is he obliged to learn? 
He said: “He cannot afford to do anything without knowledge, and he cannot avoid asking.” (Narrated by Ibn ‘Abd al-Barr in Jami’ Bayan al-‘Ilm (1/56) 
Al-Ghazali (may Allah have mercy on him) said: 
“Every person in his daily life is bound to face new issues with regard to his worship and dealings with others. So he must ask about everything, whatever new issues he encounters, and he must hasten to find out about what he expects to face before he faces it.” (Ihya ‘Ulum al-Din, 1/34) 
Our advice to those who work in trade and buying and selling is to read some of the books that have been written about the fiqh of transactions, such as al-Mulakhkhas al-Fiqhi by Shaykh Salih al-Fawzan, and Ma la Yas’u al-Tajir Jahlulu by Prof. ‘Abd-Allah al-Muslim and Salah al-Sawi. 
For more, please see this category: Business and Financial Transactions
And Allah knows best.