ANSWER:

He must ask Allah for forgiveness and be remorseful for not checking! 

A person ate pork pizza without him knowing that it was pork. Later he came to know that the meat that was used was pork. Should he ask Allah(swt) for repentance? If yes how should he feel remorse, guilt, regret for the above mentioned deed as this was by accident?

Halal/Haram Matters, Sins |