In modern Christianity, it is common for a "Christian" who has been rebuked to say something to the effect of, "Don’t judge; we’re under grace."
That kind of statement is based on a very wrong understanding of grace. The very reason that we can admonish one another is because we’re under grace. "Sin will not have power over you because you are not under law, but under grace" (Rom. 6:14).
There are four main verses I like to use to define grace properly. You just saw one of them. Grace is the power from God that causes sin to lose its power over us. Here are the others:
Similar to Rom. 6:14, the following passage tells us that grace delivers us from sin:
For the grace of God that brings salvation has appeared, teaching us that denying ungodliness and worldly lusts, we should live soberly, godly, and righteously in this present age, looking for the blessed hope and glorious appearing of our great God and Savior Jesus Christ, who gave himself for us so that he might purify for himself his own special people, zealous for good works. (Tit. 2:11-14)
This one talks about the fact that grace helps us in time of need:
Let us come boldly to the throne of grace so that we may find mercy and grace to help in time of need. (Heb. 4:16)
And finally, Peter tells us that grace is the power behind our spiritual gifts and services:
As each one has received a gift, serve it to one another, as good stewards of the manifold grace of God. If anyone speaks, let him speak as the oracle of God. If anyone serves, let it be from the ability which God provides, so that God may be glorified in all things through Jesus Christ, to whom be praise and dominion forever and ever. (1 Pet. 4:10-11)
In today’s world, we like to confuse grace with mercy. We call grace God’s unmerited favor, which may not be a bad definition if we understand favor correctly. Grace is power, and if you have grace, it will teach you to live godly, break sin’s power over you, and make you an able servant of the gifts God has given you. In fact, whatever the need, if you come boldly to the throne of God, you can find mercy from God, and you can also find grace, which will help with anything you might have need of.
It gives a little different picture of the fact that we are saved by grace. God has kindly given us access to grace through faith (Rom. 5:2), and we stand in that power by faith. That is why Paul tell us that …
By grace are you saved through faith … (Eph. 2:8)
Freely, apart from works, with all our past forgiven, we can enter into grace through faith. When we do, just as Titus 2:11-14 tells us above, we become "his workmanship, created in Christ Jesus to do good works, which God has prepared in advance for us to do" (Eph. 2:10).
We are in desperate need of the grace of God, but it is not because we need God to overlook sin which he has never promised to overlook. If we practice the works of the flesh, we will not inherit the kingdom of God (Gal. 5:19-21). If we live according to the flesh, we will die (Rom. 8:12), but we will never overcome the flesh on our own. We need the righteousness of God, those good works which God has prepared in advance for us to do, which we will only be able to do as we "by the Spirit, put to death the deeds of the body" (Rom. 8:13).
I believe that God is far more merciful than we give him credit for. Day after day, as we repent and are taught and empowered by grace, we will find his mercies new every morning. But God is not mocked. It is only as we walk in the light that we will find fellowship with one another and experience the ongoing cleansing of the blood of Jesus (1 Jn. 1:7).