'The first resurrection,' mentioned in Revelation 20:5, 6, does not mean a first resurrection, but the essence and primary part of resurrection, which is salvation and eternal life. There is only one resurrection to life. A second does not happen, and is not mentioned anywhere in the Bible.

(References: Apocalypse Explained 6; Apocalypse Revealed 851; Revelation 20:5-6)

3475. It has been stated and shown several times already that in heaven representatives like those contained in the Word are manifesting themselves constantly one after another. These representatives are such that spirits and angels see them in light far clearer than the light which shines in the world at midday. Indeed these representatives in heaven are such that all the things seen by the angels which take an outward form are also perceived by them as to the meaning which those same things carry in their inward form. And they also hold further things that are even more internal. For there are three heavens. In the first heaven an angel sees these representatives in the outward form they take, and at the same time he has a perception of the meaning which they possess in their inward form. In the second heaven an angel sees them as they exist in their inward form, and at the same time he has a perception of what they are in the form that is even more internal. In the third heaven an angel sees them as they exist in that even more internal form, which is the inmost. Things seen in the first heaven are general representations of the things seen in the second heaven; while these in turn are general representations of those seen in the third. Thus things seen in the first heaven hold within themselves those seen in the second; and those seen in the second hold within themselves those seen in the third. And since they manifest themselves by degrees as described it may be evident how perfect, how full of wisdom, and at the same time how blessed, those things are which are seen in the inmost heaven, and that they are utterly indescribable. For millions upon millions manifest themselves in one particular feature of a whole representation. Every single one of those representatives embodies such things as belong essentially to the Lord's kingdom, while these in turn embody those that belong essentially to the Lord Himself. Inhabitants of the first heaven see within their representatives such things as manifest themselves within the inner sphere of the kingdom. And within these they see things more interior still, and so, though remotely, things that are representative of the Lord. Inhabitants of the second heaven see within their representatives such things as exist in the inmost sphere of the kingdom; and within these they see representatives of the Lord more closely. Inhabitants of the third heaven however see the Lord Himself.