On the third day after the superstorm: They have washed their robes

On the third day after the superstorm, the watchman heard, Revelation 7. So he opened his Bible and read.

A Great Multitude from Every Nation

^{Revelation 7: 9} After this I looked, and behold, a great multitude that no one could number, from every nation, from all tribes and peoples and languages, standing before the throne and before the Lamb, clothed in white robes, with palm branches in their hands, ¹⁰ and crying out with a loud voice, “Salvation belongs to our God who sits on the throne, and to the Lamb!” ¹¹ And all the angels were standing around the throne and around the elders and the four living creatures, and they fell on their faces before the throne and worshiped God, ¹² saying, “Amen! Blessing and glory and wisdom and thanksgiving and honor and power and might be to our God forever and ever! Amen.”
¹³ Then one of the elders addressed me, saying, “Who are these, clothed in white robes, and from where have they come?” ¹⁴ I said to him, “Sir, you know.” And he said to me, “These are the ones coming out of the great tribulation. They have washed their robes and made them white in the blood of the Lamb.

¹⁵ “Therefore they are before the throne of God,
    and serve him day and night in his temple;
    and he who sits on the throne will shelter them with his presence.
¹⁶ They shall hunger no more, neither thirst anymore;
    the sun shall not strike them,
    nor any scorching heat.
¹⁷ For the Lamb in the midst of the throne will be their shepherd,
    and he will guide them to springs of living water,
and God will wipe away every tear from their eyes.”

________________________More verses on 'washing' and 'wearing white garments':

1 Corinthians 6:11
And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.
1 Corinthians 6:10-12 (in Context) 1 Corinthians 6 (Whole Chapter) Other Translations

Hebrews 10:22
let us draw near with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.
Hebrews 10:21-23 (in Context) Hebrews 10 (Whole Chapter) Other Translations

Acts 22:16
And now why do you wait? Rise and be baptized and wash away your sins, calling on his name.’
Acts 22:15-17 (in Context) Acts 22 (Whole Chapter) Other Translations

Ephesians 5:26
that he might sanctify her, having cleansed her by the washing of water with the word,
Ephesians 5:25-27 (in Context) Ephesians 5 (Whole Chapter) Other Translations

Isaiah 1:16
Wash yourselves; make yourselves clean; remove the evil of your deeds from before my eyes; cease to do evil,
Isaiah 1:15-17 (in Context) Isaiah 1 (Whole Chapter) Other Translations

 

Jeremiah 4:14
O Jerusalem, wash your heart from evil, that you may be saved. How long shall your wicked thoughts lodge within you?
Jeremiah 4:13-15 (in Context) Jeremiah 4 (Whole Chapter) Other Translations

 

What qualified them to wear white robes?

1. The blood of the Lamb.
2. They have not soiled their garments by sins.
3. They are considered worthy by the Lord.
4. The one who conquers (overcomes sins)
    
   Revelation 3:4-5
   Yet you have still a few names in Sardis, people who have not soiled their garments, and they will walk with me in white, for they are worthy. The one who conquers will be clothed thus in white garments, and I will never blot his name out of the book of life. I will confess his name before my Father and before his angels.
   Revelation 3:3-5 (in Context) Revelation 3 (Whole Chapter) Other Translations
   Rewards for those who get to wear white garments in heaven
   
   1. The Lord will allow them to walk with Him (in white).
      
   2. Their names will be kept in the book of life.
      
   3. Jesus will grant them to sit with Him on His throne. (Rev.3:21)
   Revelation 3:18
   I counsel you to buy from me gold refined by fire, so that you may be rich, and white garments so that you may clothe yourself and the shame of your nakedness may not be seen, and salve to anoint your eyes, so that you may see.
   Revelation 3:17-19 (in Context) Revelation 3 (Whole Chapter) Other Translations
   Revelation 4:4
   Around the throne were twenty-four thrones, and seated on the thrones were twenty-four elders, clothed in white garments, with golden crowns on their heads.
   Revelation 4:3-5 (in Context) Revelation 4 (Whole Chapter) Other Translations

 How to be sanctified?

BY THE HOLY SPIRIT AND BY THE TRUTH -THE WORD OF GOD

2 Thessalonians 2:13

[ Stand Firm ] But we ought always to give thanks to God for you, brothers beloved by the Lord, because God chose you as the firstfruits to be saved, through sanctification by the Spirit and belief in the truth.

John 17:17
Sanctify them in the truth; your word is truth.
John 17:16-18 (in Context) John 17 (Whole Chapter) Other Translations

John 17:19
And for their sake I consecrate myself, that they also may be sanctified in truth.
John 17:18-20 (in Context) John 17 (Whole Chapter) Other Translations

 ABSTAIN FROM SEXUAL IMMORALITY

1 Thessalonians 4:3
For this is the will of God, your sanctification: that you abstain from sexual immorality;
1 Thessalonians 4:2-4 (in Context) 1 Thessalonians 4 (Whole Chapter) Other Translations

THE GOD OF PEACE SANCTIFIES YOU -BY HIS (JESUS) BLOOD

1 Thessalonians 5:23
Now may the God of peace himself sanctify you completely, and may your whole spirit and soul and body be kept blameless at the coming of our Lord Jesus Christ.
1 Thessalonians 5:22-24 (in Context) 1 Thessalonians 5 (Whole Chapter) Other Translations

How much worse punishment, do you think, will be deserved by the one who has trampled underfoot the Son of God, and has profaned the blood of the covenant by which he was sanctified, and has outraged the Spirit of grace?
Hebrews 10:28-30 (in Context) Hebrews 10 (Whole Chapter) Other Translations

Hebrews 13:12
So Jesus also suffered outside the gate in order to sanctify the people through his own blood.
Hebrews 13:11-13 (in Context) Hebrews 13 (Whole Chapter) Other Translations

   BY FAITH, BELIEF, AND OBEDIENCE TO JESUS (RIGHTEOUSNESS OF GOD)

Acts 26:18
to open their eyes, so that they may turn from darkness to light and from the power of Satan to God, that they may receive forgiveness of sins and a place among those who are sanctified by faith in me.’
Acts 26:17-19 (in Context) Acts 26 (Whole Chapter) Other Translations

Romans 6:19
I am speaking in human terms, because of your natural limitations. For just as you once presented your members as slaves to impurity and to lawlessness leading to more lawlessness, so now present your members as slaves to righteousness leading to sanctification.
Romans 6:18-20 (in Context) Romans 6 (Whole Chapter) Other Translations

Romans 6:22
But now that you have been set free from sin and have become slaves of God, the fruit you get leads to sanctification and its end, eternal life.
Romans 6:21-23 (in Context) Romans 6 (Whole Chapter) Other Translations