What does Mark 9:47 mean?

While tying a millstone around our necks and throwing ourselves into the sea (Mark 9:42) or cutting off our hands and feet (Mark 9:43, 45) would, indeed, keep us from sinning with our lives, hands, or feet, this verse clearly shows that Jesus is speaking symbolically: even if you pluck out one eye, you can certainly still sin with the other. Jesus is not encouraging physical maiming. Instead, He is conveying that we should take practical—if not quite so extreme—measures to avoid sin. In Jesus' time, the eye was thought to be the source of envy and jealousy. We will always face people with more money, more popularity, more possessions, and better looks than us. We particularly need God's help to overcome sins of the mind.

In modern times, a corollary of "cutting out one eye" could be limiting internet access. Internet pornography is a serious problem with non-Christians and Christ-followers alike. It is much better to install a tracking program or avoid the internet as much as possible than to risk the hellish side of the web.

"Hell" is from the Hebrew root word geenna or Gehenna. In Jesus' time, this valley was a dump where dead animals and other disgusting things were brought to be burned. In the Old Testament, Gehenna, or the Valley of Hinnom, was where the Israelites sacrificed their children to pagan idols. They made great metal statues of the god Molech and built fires around the figures. When the metal grew so hot it glowed, the people burned their children either by placing them in the idol's outstretched arms or in a cavity specially built in the figure's torso (2 Chronicles 28:3).

In contrast, Jesus calls us to enter the "kingdom of God." Ordinarily in the New Testament, the "kingdom of God" means any time and place where God's sovereignty, power, and authority were manifest. Here, however, it means eternity in heaven.