Ibn Majah

Commentary:
Benefits and Issues:

➊
In financial transactions, any dealings that a person engaged in before accepting Islam—their mistakes are forgiven and his ownership will be considered lawful.

➋
If, before accepting Islam, a shared item was divided according to non-Islamic custom, then after accepting Islam, it will not be divided again.

➌
After accepting Islam, a Muslim is bound by Islamic laws; therefore, any division, trade, or other transaction that takes place will be examined in the light of Islamic laws, and any dealings contrary to Shariah will be declared null and void.

➍
If, before Islam, a non-Islamic transaction took place but payment was not made, then the matter will be settled in the light of Islamic law. For example, if a loan was given on interest (riba) and then Islam was accepted, now he cannot collect the interest, only the principal amount can be collected.

Benefits and Issues:
Benefit: After the advent of Islam, the actions of the pre-Islamic era (jahiliyyah) have no significance.
A person who adheres to the practices of jahiliyyah has either not accepted Islam at all,
or, if he has accepted it, then he does not consider Islam to be a religion.
Therefore, it is obligatory that after matters of belief and worship, all financial and non-financial dealings should also be conducted according to the principles of Islam.