Thematic Bible: No entrance into heaven without cleansing

Then, addressing me, one of the elders [ of the heavenly Sanhedrin] said, Who are these [people] clothed in the long white robes? And from where have they come? I replied, Sir, you know. And he said to me, These are they who have come out of the great tribulation (persecution), and have washed their robes and made them white in the blood of the Lamb.