Whenever the New Testament tells people to believe in Jesus Christ, implicit in that command is to repent of their sins. You cannot turn to trust Jesus Christ without at the same time turning from your sins. To believe on Him is to turn from all wickedness. You cannot trust without turning. 

Ezekiel 18 is a classic Old Testament passage on true repentance. In no place in the Old Testament will you a find a clearer and more thorough defense of how precious repentance is to the heart of God.

"But if the wicked man turns from all his sins which he has committed and observes all My statutes and practices justice and righteousness, he shall surely live; he shall not die. All his transgressions which he has committed will not be remembered against him; because of his righteousness which he has practiced, he will live. Do I have any pleasure in the death of the wicked," declare the Lord God, "rather than that he should turn from his ways and live?" (Eze 18:21-23).

 A man could live 70 years of wicked indulgence, cursing, swearing, murdering, and sleeping around; but if he turns from his sin, admits his wickedness, and seeks the mercy of God, he will find it! God will not turn him out! 

But God balances the equation to this scenario:

"But when a righteous man turns away from his righteousness, commits iniquity and does according to all the abominations that a wicked man does, will he live? All his righteous deeds which he has done will not be remembered for his treachery which he has committed and his sin which he has committed; for them he will die" (Eze 18:24). 

The mercy of God stands tall in this account! A man or woman could live a lifetime of evil but be forgiven at the last moment if they turn from their sin. This was the thief on the cross. But if a man or woman lives a lifetime of good deeds, but rejects God at the last moment and refused to repent, he will die in his sins and not a single good deed of his life will count in his favor. This was King Solomon. 

King Solomon lived a life of righteousness but died in his sins. The thief lived a life of wickedness but died forgiven. The difference? One was humble enough to repent and ask for mercy.