John 3:5 Jesus answered, "Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God."
Only those born of water and the Spirit can enter the kingdom of God
Born of Water
1Cor 6:9-11 Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived. Neither fornicators, nor idolaters, nor adulterers, nor homosexuals, nor sodomites, nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners will inherit the kingdom of God. And such were some of you. But you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus and by the Spirit of our God.
It is only by obeying the truth that we are cleansed with the pure water (His words) of the corruption of this world. The evidence of sanctification is the sincere love of the brethren and the love for one another fervently with a pure heart
1Pet 1:22-23 Since you have purified your souls in obeying the truth through the Spirit in sincere love of the brethren, love one another fervently with a pure heart, having been born again, not of corruptible seed but incorruptible, through the word of God which lives and abides forever,
Gal 5:19-21 Now the works of the flesh are evident, which are: adultery, fornication, uncleanness, lewdness, idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God.
Unless we crucify the flesh in sanctification we cannot enter the kingdom of God. Repentance from the above sins with bring us back to His mercy and love, and our walk with Him again.
Rom 8:5-6, 13 For those who live according to the flesh set their minds on the things of the flesh, but those who live according to the Spirit, the things of the Spirit. For to be carnally minded is death, but to be spiritually minded is life and peace... For if you live according to the flesh you will die; but if by the Spirit you put to death the deeds of the body, you will live.
Born of the Spirit
John 14:15-16,16:13 If you love Me, keep My commandments. And I will pray the Father, and He will give you another Helper, that He may abide with you forever... However, when He, the Spirit of truth, has come, He will guide you into all truth; for He will not speak on His own authority, but whatever He hears He will speak; and He will tell you things to come."
If we keep His commandments, we will make the Holy Spirit (Jesus Christ) dwelling in us to be our King thus establishing the kingdom of God within us. The Spirit of truth will then guide and lead us into all truth and set us free from the snares and bondages of this world.
Luke 17:20b-21 "The kingdom of God does not come with observation; nor will they say, 'See here!' or 'See there!' For indeed, the kingdom of God is within you."
Remember these brethren will enter the kingdom of God, Then He lifted up His eyes toward His disciples, and said: "Blessed are you poor, for yours is the kingdom of God... But love your enemies, do good, and lend, hoping for nothing in return; and your reward will be great, and you will be sons of the Most High. For He is kind to the unthankful and evil. Therefore be merciful, just as your Father also is merciful." (Luke:6.20, 35-36)