When we are without God, we can get ourselves into some very complicated positions.  Actually, the Word of God has little to say about an incident like this, so let’s see if we can find some biblical principles that would apply to this situation. 

From what you wrote, I assume this man was married and committed fornication against his wife before he came to know the Lord Jesus Christ as his savior.  It is a terrible thing to vow to be faithful to one person, and then to break that vow.  For a believer or an unbeliever, this is a terrible thing that has many long-term consequences. 

After his divorce, this man married another woman and had children with her.  It was after he entered into this marriage that he trusted in the Lord as his savior.  I am very thankful that he finally saw his need of a savior and turned to the Lord.  No matter what his background was, the Lord promises in John 6:37, “…him that cometh to me I will in no wise cast out.”  The Lord will not reject any repentant sinner who puts their faith in Him. 

I’m not sure about his pastor’s counsel.  A wedding ceremony is not really the place for public confession.  In fact, since this man has already married his second wife, I see no need for a separate wedding ceremony at all, unless they would like to have one since they were not saved when they first married. 

Since this man is now a believer in the Lord, I trust that he has already confessed his sin of fornication to the Lord and to his first wife.  In Psalm 51, we have David’s confession to the Lord for his act of fornication with Bathsheba.  I encourage you to read that entire chapter to see David’s true remorse for his sin.  He said in verses 2-4, “Wash me throughly from mine iniquity, and cleanse me from my sin. For I acknowledge my transgressions: and my sin is ever before me. Against thee, thee only, have I sinned, and done this evil in thy sight: that thou mightest be justified when thou speakest, and be clear when thou judgest.”  This is the voice and heart of a truly repentant man.  If you are close to your friend, I encourage you to read this to him and share David’s heart with him.  I trust he will have a similar heart of repentance towards the Lord and his ex-wife. 

Since the term “spiritual wedding” is not found in the Bible, I’m not sure what this pastor considers it to be.  For me, a spiritual wedding is one that invites the Lord into the marriage and vows are made before Him and to Him.  It is a wedding where the Lord leads and will include instruction to the couple from God’s Word concerning their marriage.  It will be a ceremony steeped in prayer.  As I said earlier, since this couple is already married, this ceremony is not necessary unless they want to spiritual wedding.  Of course, it would not be a legal affair since the state already recognizes them as married.  It will just be ceremonial.  As far as a public confession to the congregation, I don’t see that as necessary at all.  If this man has confess to the Lord and to his ex-wife, he has been forgiven and since being saved, he is “a new creature: old things are passed away; behold, all things are become new.” (2 Corinthians 5:17).  (377.2)