The number three in the Bible represents completeness. That's why Jesus rose on the third day after the Crucifixion -- his transformation was complete. It's why Elijah stretched himself on the dead child three times, why Jonah was in the belly of the fish for three days, why the Lord called Samuel three times, and many more. It's also reflected in the fact that there are three levels of heaven, three levels of hell, three levels to human life and, ultimately, three aspects of the Lord Himself: Father, Son and Holy Spirit.

'The plagues of Egypt' signify the falsities and lust which cause the church to perish.

In Revelation 16, 'the plagues were poured out upon men by angels from heaven' when they were truths and goods sent down by the Lord which were turned into evils and falsities by the people who were below. 'Plagues' signify evils of love, and falsities of faith.

(Odkazy: Apocalypse Revealed 656)