Many people are familiar with John 3:16, "For God so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life." One could think of this believing as something that "I have to do myself" to prove love for God. Yet if you read on in that passage, in verse 21 it explains that "Whoever does what is true comes to the light, so that it may be clearly seen that his works have been carried out in God." The key phrase is carried out in God. Martin Luther talks about how God works in our lives:
A theology of glory calls evil good and good evil. A theology of the cross calls the thing what it actually is.
This is clear: he who does not know Christ does not know God hidden in suffering. Therefore he prefers works to suffering, glory to the cross, strength to weakness, wisdom to folly, and, in general, good to evil. These are the people whom the apostle calls "enemies of the cross of Christ" (Phil. 3:18), for they hate the cross and suffering and love works and the glory of works. Thus they call the good of the cross evil and the evil of a deed good. God can be found only in suffering and the cross, as has already been said. Therefore the friends of the cross say that the cross is good and works are evil, for through the cross works are destroyed and the old Adam, who is especially edified by works, is crucified. It is impossible for a person not to be puffed up by his good works unless he has first been deflated and destroyed by suffering and evil until he knows that he is worthless and that his works are not his but God's.