To be "justified" is to be declared "just" or "righteous" by God. We know that only those who are righteous will have eternal life:
25 And behold, a lawyer stood up to put him to the test, saying, “Teacher, what shall I do to inherit eternal life?” 26 He said to him, “What is written in the Law? How do you read it?” 27 And he answered, “You shall love the Lord your God with all your heart and with all your soul and with all your strength and with all your mind, and your neighbor as yourself.” 28 And he said to him, “You have answered correctly; do this, and you will live.”(Luke 10:25-28)We also know there no righteous human beings.
“None is righteous, no, not one; no one understands; no one seeks for God. All have turned aside; together they have become worthless; no one does good, not even one.” “Their throat is an open grave; they use their tongues to deceive.” “The venom of asps is under their lips.” “Their mouth is full of curses and bitterness.” “Their feet are swift to shed blood; in their paths are ruin and misery, and the way of peace they have not known.” "There is no fear of God before their eyes.”
Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God. For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin. (Romans 3:10-20)
So there is a big problem. How is it possible for any human being to be declared just before God?
The Doctrine of "Justification" is the doctrine that explains what God has done to give us that righteousness we do not naturally possess.
This week's podcast discusses this doctrine and answers a question about it that came up on Sunday:
here also is part (about 5 minutes) of a video lecture by RC Sproul addressing the same topic. The video looks like it was made in the 80's so try to look past the hair. It's good stuff.