In Leviticus 13:46, this signifies to be led by the Lord as celestial men no longer infested by evil spirits. (Arcana Coelestia 139)

In Isaiah 4:5, this signifies the good of the celestial church protected so that it is not damaged from too much light or shade. (Apocalypse Explained 594[15])

139. In ancient times those who were guided as celestial people by the Lord were said 'to dwell alone', for the reason that evil forces, or evil spirits, were infesting them no longer. This was also represented in the Jewish Church by their dwelling alone after the nations had been driven out. For this reason several times in the Word the Lord's Church is described as 'alone', as in Jeremiah,

Rise up, go up against a nation at ease that dwells securely. It has no gates or bars; they dwell alone. Jeremiah 49:31.

In the prophecy of Moses,

Israel dwelt securely, alone. Deuteronomy 33:28.

And plainer still in Balaam's prophecy,

See, a people, it dwells alone, and is not reckoned among the nations. Numbers 23:9.

Here 'nations' stands for evils. These descendants of the Most Ancient Church did not wish to dwell alone; they did not wish to be a celestial man, that is, to be guided as a celestial man by the Lord, but to be among the nations, as also did the Jewish Church. And since this was what they desired it is said, 'It is not good that the man should be alone'. Indeed when this is what a person desires, he is already under the influence of evil, and his wish is granted.