and are justified by his grace as a gift, through the redemption that is in Christ Jesus, (ESV)
The most amazing word in this verse is the word "gift." The fact that we can be justified before God is amazing. Redemption is hard enough to believe but we can maybe accept it. The word that is most difficult is the word "gift." If you doubt me I pray that you will meet some people who are still unbelievers for one reason; they refuse to have God's redemption as a gift.
The fact that God would simply give us a right relationship with him based on his work and his work alone is hard for us to accept. We want to work for what we receive. We have a hard time simply receiving something from someone without doing at least something in return. God says, "Do you want to be made right with me? You cannot earn it. You must simply receive it."
Let's look at some of the other words in this verse. What does it mean to be justified. Justification is the work in which God declares us to be made right with him. This is substantial when we consider that before this act of God we were described as sinners, rebels, murderers, thieves, haters of God, etc. Our sinful condition, without God's justification, renders us in eternal judgment.
Redemption is best understood in the context of slavery. All of us are born as slaves to sin. Our horrible slave master is none other than Satan himself. Redemption is the act whereby we are bought by the blood of Christ and set free from slavery. Our debt has been paid. We no longer have to live according to what Satan demands.
Justification and redemption are wonderful things but are only realized by those who receive them as a free gift. If you are trying to work for them you will never have them. Accept his gift by repentance and faith today!