It is befitting for a trader to learn the laws (aḥkām) of buying and selling concerning issues he commonly encounters. In fact, if he would be at risk of committing an unlawful (ḥarām) act or abandoning an obligatory (wājib) act as a result of not learning the laws, then it would be necessary [not just befitting] for him to learn them. It is reported that His Eminence Imam al-Ṣādiq (ʿA) said, ‘One who wishes to engage in buying and selling must learn its laws.
If he were to buy and sell before learning its laws, he would fall into ruin by means of invalid (bāṭil) and dubious transactions (muʿāmalāt).’