"The punishment of those who wage war against Allah and His Messenger, and strive with might and main for mischief through the land is: execution, or crucifixion, or the cutting off of hands and feet from opposite sides, or exile from the land: that is their disgrace in this world, and a heavy punishment is theirs in the Hereafter;" - Quran 5:33 (read more)

"O Allah's Apostle! We asked you for mounts, but you took an oath that you would not give us any mounts; we think that you have forgotten your oath.' He said, 'It is Allah Who has given you mounts. By Allah, and Allah willing, if I take an oath and later find something else better than that. then I do what is better and expiate my oath.'" - Sahih Bukhari 7:67:427 (read more)

"If anyone rejects the [uncurrupted] message of Jesus (peace be upon him) or the [uncurrupted] message of Moses (peace be upon him) or the message of Muhammad (peace and blessings of Allaah be upon him), he is a kaafir (disbeliever). If anyone denies that this Qur’aan was revealed from God, or mocks it, he is a kaafir, because the Qur'aan was revealed from Allaah." - Islam Q&A