How can a human being have free will despite God's foreknowledge of what they will choose, and if everything is predetermined, why is a person punished for their actions?

The Muslim rejects protesting by divine decree (qadar) when committing a sin, yet does not mind attributing good deeds to himself and hoping for reward for them. This is a contradiction. If someone aggresses against him, he does not protest by divine decree but demands retribution (qisas), which indicates that the action is volitional. Allah knew what the servant would do by his own choice and created for him the ability and will to act. He sent messengers to establish the proof, so His servants have no argument against Allah. The hadiths that speak of the vastness of Allah's mercy are to encourage repentance, not to justify sin. Whoever persists in sin exposes himself to Allah's punishment.