(Rev. 19:7 KJV) 7 Let us be glad and rejoice, and give honour to him: for the marriage of the Lamb is come, and his wife hath made herself ready.
The Bride of Christ is the Church.
Paul tells us this in his letter to the Corinthians.
(2 Cor. 11:2 KJV) 2 For I am jealous over you with godly jealousy: for I have espoused you to one husband, that I may present you as a chaste virgin to Christ.
They were redeemed from all nations.
(Rev. 5:9-10 KJV) 9 And they sung a new song, saying, Thou art worthy to take the book, and to open the seals thereof: for thou wast slain, and hast redeemed us to God by thy blood out of every kindred, and tongue, and people, and nation;
10 And hast made us unto our God kings and priests: and we shall reign on the earth.
This would include Tribulation Saints.
(Rev. 7:9 KJV) 9 After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands;
His wife hath made herself ready – through obeying God and living holy and are sanctified.
(Eph. 5:25-26 KJV) 25 Husbands, love your wives, even as Christ also loved the church, and gave himself for it;
26 That he might sanctify and cleanse it with the washing of water by the word,
They’ve kept their lamps filled and wicks trimmed, ready for the marriage.
(Matt. 25:1-13 KJV) Then shall the kingdom of heaven be likened unto ten virgins, which took their lamps, and went forth to meet the bridegroom.
2 And five of them were wise, and five were foolish.
3 They that were foolish took their lamps, and took no oil with them:
4 But the wise took oil in their vessels with their lamps.
5 While the bridegroom tarried, they all slumbered and slept.
6 And at midnight there was a cry made, Behold, the bridegroom cometh; go ye out to meet him.
7 Then all those virgins arose, and trimmed their lamps.
8 And the foolish said unto the wise, Give us of your oil; for our lamps are gone out.
9 But the wise answered, saying, Not so; lest there be not enough for us and you: but go ye rather to them that sell, and buy for yourselves.
10 And while they went to buy, the bridegroom came; and they that were ready went in with him to the marriage: and the door was shut.
11 Afterward came also the other virgins, saying, Lord, Lord, open to us.
12 But he answered and said, Verily I say unto you, I know you not.
13 Watch therefore, for ye know neither the day nor the hour wherein the Son of man cometh.
This means living a life of holiness.