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.

9419. 'And Moses rose up, and Joshua his minister' means the Word and its representative. This is clear from the representation of 'Moses' as the intermediary between the Lord and the people who are restricted to the outward sense of the Word, separated from the inward, thus also as the Word, as accords with what has already been shown just above in 9414; and from the representation of 'Joshua his minister' as its representative. The reason why 'Joshua' here means that representative is that what is representative serves and ministers, in order that the outward things of the Word and of worship may present themselves to the Lord through the intermediary, who was Moses. But these are matters such as are scarcely intelligible except to those who know about the ways in which a representation of the outward or literal sense of the Word is accomplished in heaven. That is to say, it is represented in one way with those who are acquainted with the outward sense of the Word and at the same time with the inward, that is, those who are acquainted with the outward sense of the Word and at the same time with true teachings of the Church, and in another way with those restricted to the outward sense, separated from the inward, as with this people. How it was accomplished with this people, see 4311.

[2] Some idea may be formed from this regarding the intermediary that 'Moses' represents and the ministering representative that 'Joshua' represents. That is to say, there is an inward holiness which Divine Truth emanating from the Lord possesses, thus which the Word and worship springing from it possess. This flows into heaven and is received there by angels. There is also an inflow of holiness indirectly through that inward holiness, as well as directly from the Lord, to good spirits present with a person engaged in reading the Word or in worship springing from it. This holiness is called an outward holiness, and when it flows in with a person it produces representative images formed in accord with the correspondences known to the person. All this helps one to see what use the intermediary serves, which Moses represents now, and what use the minister serves, which Joshua represents, namely that the outward holiness acts as intermediary, while the representative existing on the lowest level of order acts as minister. But it should be recognized that the idea of Divine Truth flowing in is unintelligible to a person unless the Lord sheds light on the idea. For the person sees what happens in no other way than this, that the holiness of the Word and the holiness of worship flows from the person to the Lord. But this order is inverted order, and is called physical influx, which is an appearance and not at all the reality; see what has been shown in the places referred to in 9223, 9227 (end).