7. Let us rejoice and be glad and give glory to Him -

the faithful are happy. They want to give praise to God.

for the marriage of the Lamb has come and His bride has made herself ready. -

This is the climax of our relationship with Christ. That when the marriage takes place in heaven, when we are joined to Him for eternity. In marriages there were three parts, the betrothal, interval, marriage - which was the climax. The betrothal was an announcement that expressed the desire of marriage, to commit oneself to the other person. We become betrothed to Christ when we commit ourselves to Him at baptism. He already has paid the dowry. The interval was a time of growing relationships between the two betrothed so that people involved will be best suited for each other
when the marriage comes. Christ has already done His part to have the required relationship and now we are left to do our part. We do thisby remaining faithful in our lives. When we do this we are best suited to take part in the marriage feast at the end. Then comes the marriage, the climax. A life together in eternity with Christ. This is what is being celebrated here in Chapter 19. This helps explain why they are so happy. What a climax.

8. And it was given to her to clothe herself…righteous acts of God. -

it is given to the faithful to do faithful deeds in the interval of the marriage. The marriage has already begun in the life of every Christian. The climax happens in Heaven.

9. And he said to me, “Write, -

this is for assurance.

Blessed are those who are invited to the marriage supper of the Lamb.” -

they are blessed because they were invited but most of all because they responded to the invitation.

And he said to me “These are true words of God.” -

that which was written is the true words of God. Surely they can be used for assurance purposes.

10. And I fell at his feet to worship him -

John thought that he was before God. This is why he fell to worship him.

And he said to me, “Do not do that; I am a fellow servant of yours…of Jesus, -

This is one of those who had remained faithful. This would be a comfort to know that someone already had remained faithful. A fellow servant. It can be done.

worship God.” -

God alone is worthy of worship,not us, even though we are faithful till the end.

For the testimony of Jesus is the spirit of prophecy -

this is a faithful life bearing testimony of Jesus Christ as the son of God.