A man once told me he wished he could marry several wives claiming he was joking. The fact that he would joke about it revealed to me that it was a desire of his heart.
If someone desires to have more than one wife then there is adultery in that man's heart. To have a second wife is adultery on the first wife.
Even if someone does not commit adultery in actions but still desires to do so then it is the same as if they had done the act. God looks at the heart first even before sin becomes an action.
This is why it is almost laughable when a so-called Christian is acting sinfully and claiming we should not judge their actions because in their heart they are a good person.
The fact is that if we merely desire something in our hearts it is the same as committing sin in the flesh.
Matthew 5:27-28 "27 You have heard that it was said, ‘Do not commit adultery.’ 28 But I tell you that anyone who looks at a woman to lust after her has already committed adultery with her in his heart. "
Those who say we cannot judge someone's outward sin because we do not know their heart is denying God's truth that we know their heart by their actions.
Having chastised a group of Christian women who were wearing bikinis on the beach, I was told I was sinning by judging them. All I did was tell them they should not be displaying their bodies in this way while romping on the beach with young men. They were making people pyramids on the beach women climbing on men and flaunting it in pictures on Facebook.
When I chastised the youth group leader for not speaking to the young women about this she rebuked me for judging and claimed these were girls with good hearts. My response was that if the girls had good hearts then they would happily receive correction about their clothing and change their dress.
Someone who is scantily clad on the beach is displaying their heart. Modest humble people cannot dress recklessly in front of men, they would guard their own hearts and the hearts of any men looking at them. A modest humble person desiring God would be ashamed when corrected and learn from it.
Only a rebellious prideful woman would fight back to defend their wicked clothing style. I would never correct a non-believer about their clothing, the gospel would be the focus. But for those who claim to be Christian, it is commanded to rebuke immoral behavior, even having nothing to do with them if they will not be repentant.
When a woman has gone to the length of dressing provocatively in front of men she has had lust in her heart and desires to entice men even before she puts on those clothes and before she goes in public that way.
Proverbs 6:25
"Do not lust in your heart for her beauty or let her captivate you with her eyes." Just desiring another person's spouse is adultery without an act being committed.
Jeremiah 29:13
"13 And you will seek Me and find Me when you search for Me with all your heart."
When we are seeking Christ with all our hearts we will hate sin in our thoughts before it becomes an action. The actions show what is in the heart. The actions cannot be different from what's in the heart.
I was once told by someone that a person is not a liar just because they told one lie. My answer and God's answer was; "a person who is not a liar couldn't even tell one lie." If we have lied then we have deception in our hearts.
We have all lied at times, even small ones to save our bacon, but when we confessed it we were cleansed and want to not live a lifestyle of lies. The unbeliever fights to defend their lies, the born-again believer confesses them to be cleansed and hates the thought of ever lying again.
Romans 3:3-4 "…3What if some did not have faith? Will their lack of faith nullify God’s faithfulness? 4 Certainly not! Let God be TRUE and every man a liar. As it is written: “So that You may be proved right when You speak and victorious when You judge.” "
If someone is young in the faith the solution is not to just let all their sinful actions be ignored. The answer to someone who is young in the faith is to address what is sin in their lives and encourage them to seek God for forgiveness.
Proverbs 27:5
"Better is open rebuke than hidden love."
Matthew 18:15-17
"“If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother. But if he does not listen, take one or two others along with you, that every charge may be established by the evidence of two or three witnesses. If he refuses to listen to them, tell it to the church. And if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector."
1 Timothy 5:20
"As for those who persist in sin, rebuke them in the presence of all, so that the rest may stand in fear."
There are many more scriptures that deal with what to do when a Christian brother or sister sins. We are responsible to help others grow in the faith, if we neglect this we are sinning through fear of man. When sin is in the bodies it grows, and weaker believers will be influenced to sin too.
1 Corinthians 5:6 "Your boasting is not good. Do you not know that a little leaven leavens the whole lump of dough?"
A sin that is ignored in the body causes others in the group to sin, this is why we see so much sin in the body today. Many churchgoers live in fear of offending man without any fear of offending God.
The solution to this whole matter of disobedience to God is for believers to confess to be cleansed and seek the Lord to remove from their hearts any desire to sin.
1 John 1:9 "9 If we confess our sins, He is faithful and righteous, so that He will forgive us our sins and cleanse us from all unrighteousness."
Those who refuse to confess will not grow in holiness and will infect the body of Christ, they must be removed if they will not obey God.
1 Corinthians 5:12-13 "…12 What business of mine is it to judge those outside the church? Are you not to judge that inside? 13 God will judge that outside. “Expel the wicked man from among you.”"
Yes, God actually tells us to rebuke and expel someone who claims to be a Christian who will not repent of their sin.