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.

1487. That 'Jehovah struck Pharaoh with great plagues' means that facts were destroyed is clear from the meaning of 'Pharaoh' as knowledge in general, and therefore as the facts that constitute that knowledge, and from the meaning of 'being struck by plagues' as being destroyed. With regard to facts, these are acquired in childhood with no other end in view than that of knowing. In the Lord's case they were acquired out of delights in and affection for truth. The facts that are acquired in childhood are very many indeed, but the Lord arranges them into order, so that they may serve a use - first to enable the person to think; then so that through his thinking those facts may be of use; and at length so that the following may be accomplished, namely, that his very life may consist in use and be a life of uses. These are the things effected by the facts which he absorbs in childhood. Without them his external man could not possibly be joined to the internal and at the same time become use incarnate. When a person becomes such, that is, when all that he thinks stems from use as an end and all that he does is for the sake of use - if not by reflecting openly yet by doing so silently from a disposition acquired from reflecting openly - the facts which have served the first use, that a person may become rational, are now destroyed since they serve no further use; and so on with other facts and the uses they serve. These are the things meant here by the statement 'Jehovah struck Pharaoh with great plagues'.