'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.

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

7035. 'Israel is My son, My firstborn' means that those guided and governed by spiritual truth and good have been adopted. This is clear from the meaning of 'son', when used by Jehovah or the Lord to speak of those who belong to the spiritual Church, as one who has been adopted, dealt with below; from the meaning of 'firstborn' as the faith that is wedded to charity, which the spiritual Church possesses, dealt with in 367, 2475, 3725, 4925, 4926, 4928, 4930; and from the representation of 'Israel' as the spiritual Church, dealt with in 6637. 'Israel is My son, My firstborn' means that those guided and governed by spiritual truth and good - that is, those belonging to the spiritual Church - have been adopted and so recognized as sons because the Lord saved them by His Coming into the world, see 6854, 6914. For this reason also, as well as by virtue of their faith in the Lord, they are called 'the firstborn son'; and they are the ones who are meant by the Lord in John,

And other sheep I have which are not of this fold; I must bring them also, and they will hear My voice, and there will be one flock and one Shepherd. John 10:16.