The only reward of those who make war upon Allah and His messenger and strive after corruption in the land will be that they will be killed or crucified, or have their hands and feet on alternate sides cut off, or will be expelled out of the land. Such will be their degradation in the world, and in the Hereafter theirs will be an awful doom. -- Quran 5:33
Is it cruel? Read the verse in its context. Take your time. Think about it. Talk to your friends and fellow believers, and then let me know.
(I’m especially interested in what the Christians think about it. But Muslims can chime in as well.)