There are three things a person needs to know in order to become a Christian and then live a fulfilling life in Christ.
1) You need to know you are a sinner
The Gospel begins with the bad news that we’re all sinners:
All have sinned and fall short of the glory of God. (Rom 3:23)
There is none righteous, no, not one. (Rom 3:10)
And our sin places us under God’s judgment:
The wages of sin is death… (Rom 6:23)
We often make the mistake of comparing ourselves to other people. When we do that we convince ourselves that we aren’t so bad. But it’s “the glory of God” that we fall short of. God compares our behavior to His own — not other people — and all of us fall short when held to this standard.
Why this is important to know: 1) We must recognize that we need be saved from our sins in order to be at peace with God and 2) That salvation must come from a source outside of us because we can’t live up to God’s standard.
2) You need to know how you can be forgiven for your sins
After laying out the problem, the Gospel then give us the solution to the problem of sin:
The gift of God is eternal life in Christ Jesus our Lord. (Rom 6:23)
Christ Himself fulfilled all that God has required in His Law, and paid for our sins:
What the law was powerless to do in that it was weakened by the sinful nature, God did by sending his own Son in the likeness of sinful man to be a sin offering. (Rom 8:3)
We are saved through Christ’s work, not our own:
It is by grace you have been saved, through faith—and this not from yourselves, it is the gift of God— not by works, so that no one can boast. (Eph 2:8-9)
As we learned above, we can’t save ourselves from our sin because our good works can’t live up to God’s standard, but where our works are stained with sin and rejected, Christ’s work is perfect and is accepted.
When we say we recognize our need to be saved, and call on Christ to be our Savior, we mean we’re relying on His sacrifice to be a payment for our sins and to make peace with God on our behalf. When we do this God credits Christ’s perfection to us, we’re justified, and we’re forgiven for our sins.
Why this is important to know: Because only Jesus can save us from the penalty of our sin, any other way we try to make peace with God will fall short (Acts 4:12).
3) You need to know how you should respond to God’s forgiveness
Once we are at peace with God, through Christ, we are a new creation:
If anyone is in Christ, he is a new creation; old things have passed away; behold, all things have become new. (2 Cor 5:17)
We no longer live for sin, we live for God:
Do not present your members as instruments of unrighteousness to sin, but present yourselves to God as being alive from the dead, and your members as instruments of righteousness to God. (Rom 6:13)
You are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light. (1 Pet 2:9)
And our lives should bear good fruit:
The fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law. (Gal 5:22-23)
Why this is important to know: In order to grow in Christ we need to know how to respond to God’s grace. What Christ has done for us effects how we live. We do good works, not to be saved, but because Christ has saved us (Eph 2:10). We forgive because Christ has forgiven us (Matt 6:12). We bless because Christ has blessed us (Eph 1:3). We served because Christ has served us (Mrk 10:45). We love because Christ has loved us (1 Jhn 4:19).