In Luke 10, there's a brief exchange between Jesus and a lawyer that sets the stage for Jesus to tell the famous parable of the Good Samaritan.

The lawyer asks Jesus what he must do to inherit eternal life. Jesus seems to realize that the lawyer really knows the answer already, and - indeed he does. It's one of the pithiest, most direct instructions in the whole of the Word. Here's how the lawyer states it:

"Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy strength, and with all thy mind; and thy neighbour as thyself."

Jesus simply says to him, "Thou hast answered right: this do, and thou shalt live."

So, we know what to do: Love God. Love our neighbors. We can talk a lot about how best to do that, but the "what" is plainly stated here - and it's plainly linked to the idea of eternal life.

(Verweise: Deuteronomy 6:5; Mark 12:33)