"So God gave them" i.e., He granted them "the reward of this world and the best reward of the Hereafter." As for the reward of this world, it is victory over their enemy, and as for the reward of the Hereafter, it is Paradise.

Muhammad said: "And their saying was not" can be read both in the nominative (rafa') and the accusative (nasb). Whoever reads it in the nominative makes the predicate of "kana" (was) that which comes after "illa" (except). In speech, it is more frequent that the subject is what comes after "illa," so the meaning would be: "And their saying was nothing but their seeking forgiveness."