Is it better for a person who has committed a sin necessitating a حدّ (prescribed punishment), such as murder or cutting off a hand, to surrender themselves to the Caliph or the judge for the حدّ to be carried out upon them, or to seek Allah's forgiveness and participate in fighting the polytheists, especially if the battle is about to begin?

If an enemy invades a country, Muslims are obligated to engage in jihad, repel the aggression, and defend their sacred sites. As for someone who has committed a hadd (a crime with a prescribed punishment), they must repent and seek forgiveness. It is preferable for them to conceal their deed and not disclose it to a judge. If the matter involves the rights of another person, they should seek forgiveness or agree upon compensation. The Prophet, peace and blessings be upon him, said: "Forgive each other the hudud among yourselves. For whatever hadd reaches me has become obligatory."