To condemn the world gives to the English reader a stronger impression than that of the original Greek. The word (κρίνω, krino, the Latin c(k)erno, and the English dis-cern) means originally to separate, and in the moral sense to separate good from evil. Passing from the act to the effect, it may mean to absolve; but as the usual effect of separation is to exclude the evil, the word has attached to itself more frequently the idea of condemnation. Our word judge, which has itself something of this double meaning, is probably the best rendering in this context.
Part of the current belief about the Messiah’s advent was, that he would destroy the Gentile world. The authorised expositions of many texts of the Old Testament asserted this, and Nicodemus must ofttimes have heard it and taught it. God’s love for, and gift to, the world has just been declared. This truth runs counter to their belief, and is now stated as an express denial of it. The purpose of the Messiah’s mission is not to judge, but to save. The latter clause of the verse changes the order of the thought. It would naturally be “but that He might save the world.” The inversion makes prominent the action of man in willing to be saved.