What is the ruling on the money that your brother receives from his work after claiming an injury at work when he was not injured during work, and what is the ruling on your eating from what he buys with this money?

If the salary was disbursed based on a false claim of falling during work, then it is fraud and it is not permissible to take it. However, if it was disbursed based on a medical report stating his unsuitability for work, and the contract obliges the employer to pay his salary during illness, then there is no harm in it. As for the items he brings, there is no harm in benefiting from them, because the sin of it lies with the one who earned it, and it reached you through a permissible means (a gift). The proof for this is that the Prophet, peace and blessings be upon him, bought and ate from people who earned their living unlawfully.