Why Does the Lord Jesus Judge Man When He Returns? How Will He Judge Man?

One day, during my spiritual devotion, I saw the words of the Lord Jesus: “I am come a light into the world, that whoever believes on me should not abide in darkness. And if any man hear my words, and believe not, I judge him not: for I came not to judge the world, but to save the world. He that rejects me, and receives not my words, has one that judges him: the word that I have spoken, the same shall judge him in the last day” (John 12:46–48). Pondering over this passage of scripture, I saw that the Lord’s will and demands of us are to have us follow His words in everything and do as He asked. In my mind, since the Lord Jesus has absolved our sins, we have already been saved by grace when accepting His salvation, and will be directly taken into the kingdom of heaven when He returns. But here, why did the Lord say whoever disobeyed His words would be judged in the last days? Why would the Lord judge us?