Four areas of grace
1. Grace in salvation
Matt 26:39: He went on a little farther and bowed with his face to the ground, praying, "My Father! If it is possible, let this cup of suffering be taken away from me. Yet I want your will to be done, not mine."
John 19:30: When he had received the drink, Jesus said, "It is finished." With that, he bowed his head and gave up his spirit.
Rev 21:6: And he said to me, “It is done! I am the Alpha and the Omega, the beginning and the end. To the thirsty I will give from the spring of the water of life without payment.
These verses are talking about the idea of salvation as a gift. If you look at the way Christianity talks about salvation analytically, then it seems to have the following structure:
1) People are unable to treat others in the way that they would ideally like to be treated. It is simply impossible for anyone to do this, and it stops us from entering into eternal life with God
2) God solves this problem on the cross by Himself; we don't contribute at all to the solution
3) If you want to go to heaven you can either trust in your own goodness to get you there, or trust in what God has done for you on the cross. If you trust in the latter, then you will go to heaven
The concept of grace is closely linked to the concept of a free gift that you do nothing to earn. Salvation in Christianity is like this.
2. Grace in accepting salvation
Eph 2:4: But because of his great love for us, God, who is rich in mercy, made us alive with Christ even when we were dead in transgressions--it is by grace you have been saved.
Rom 11:6: But if it is by grace, it is no longer on the basis of works; otherwise grace would no longer be grace.
Let's say you have two friends, neither of whom are Christian, and one of them is arrogant and inconsiderate, and the other is as sweet as an angel. It would be very tempting only to talk about Jesus to the second person. That's because we tend to think that salvation is partly based on works. That is, if you're nice, trusting, considerate, don't think about things too much, and so on, you're more likely to become a Christian. One way of describing this attitude is that salvation is earned by having a good (or convenient) personality.
The passages above contradict such a view. They imply that God cares about everyone so much that He prevents a person's personality and character from getting in the way of their entering the Kingdom of God. God does this so effectively that no one receives an advantage from their personality and character over anyone else when it comes to accepting Christ. How does that work, you might ask? I don't know. But it's what scripture teaches.
3. Grace in producing works
Philippians 1:6: And I am certain that God, who began the good work within you, will continue his work until it is finally finished on the day when Christ Jesus returns.
Heb 13:21: may he equip you with all you need for doing his will. May he produce in you, through the power of Jesus Christ, every good thing that is pleasing to him. All glory to him forever and ever! Amen.
When Christians do things that please God it is because of God's gift of His Son, because God has changed them and worked through them. So they are like a gift in that God ultimately has the credit (glory) for them.
4. Grace in God doing all the protective work regarding the faith of any Christian
1 Cor 10:13: No temptation has seized you except what is common to man. And God is faithful; he will not let you be tempted beyond what you can bear. But when you are tempted, he will also provide a way out so that you can stand up under it.
Sometimes Christians can think of themselves as superior to those who have left the faith because of problems they have coped with. But this is not a scriptural attitude. No Christian protects their own faith, if the Bible is accurate. God is always the one doing the protecting, whenever someone's faith is being protected. Since Christians do not protect their own faith (according to the Bible) no one can boast about this. Every Christian will encounter challenges to their faith (which is meant to ultimately help Christians if they bear up under it), and the only thing that will keep it is taking the 'way out' that is mentioned above.