"10As it is written, There is none righteous, no, not one:
11There is none that understandeth, there is none that seeketh after God.
12They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one.
13Their throat is an open sepulchre; with their tongues they have used deceit; the poison of asps is under their lips:
14Whose mouth is full of cursing and bitterness:
15Their feet are swift to shed blood:
16Destruction and misery are in their ways:
17And the way of peace have they not known:
18There is no fear of God before their eyes"
-Romans 3:10-18
Every human being has sinned even Christians sin. Just because someone is a Christian does not mean that they will never sin again. But Jesus Christ (God in the flesh) died for our sins. He bore our sins. And the only way that we can be forgiven is through Jesus Christ. The Word of God says:
"For whosoever shall call upon the name of the Lord shall be saved."
-Romans 10:13
That does not mean that you just pray a prayer and then keep living like the world. That also does not mean that you have to work to be saved. We are saved by grace not by works.
8For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9Not of works, lest any man should boast."
-Ephesians 2:8-9