When Christ began to preach the gospel, He preached:
17 From that time
Jesus began to preach, saying,
“Repent, for the kingdom of heaven is at hand.”
In Mark:
15 and saying,
“The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.”
“Repent, for the kingdom of heaven is at hand.”
www.biblegateway.com
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So, as you can see, we must
repent and believe.
The summary in 1rst John on this:
8 If we claim to be without sin, we deceive ourselves and the truth is not in us. 9 If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness. 10 If we claim we have not sinned, we make him out to be a liar and his word is not in us.
The Incarnation of the Word of Life - That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked at and our hands have touched—this we proclaim concerning the Word of life. The life appeared; we have seen it and testify to it, and we proclaim...
www.biblegateway.com
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Consider what Christ taught is needed -- admitting we are sinners:
9 To some who were confident of their own righteousness and looked down on everyone else, Jesus told this parable:
10 “Two men went up to the temple to pray, one a Pharisee and the other a tax collector.
11 The Pharisee stood by himself and prayed: ‘God, I thank you that I am not like other people—robbers, evildoers, adulterers—or even like this tax collector.
12 I fast twice a week and give a tenth of all I get.’
13 “But the tax collector stood at a distance. He would not even look up to heaven, but beat his breast and said,
‘God, have mercy on me, a sinner.’
14 “
I tell you that this man, rather than the other, went home justified before God. For all those who exalt themselves will be humbled, and those who humble themselves will be exalted.”
If we believe
but do not admit to being a sinner, we'd be like the pharisee in Luke 18 above.
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@tonychanyt in case you are interested in more passages.