... εγω εν τω πατρι μου και υμεις εν εμοι καγω εν υμιν
[John 14:20 TR, undisputed]
... I (am) in my Father, and ye in me, and I in you.
[John 14:20 KJV]
Previously, Jesus has said (John 14:10) :
... I am in the Father, and the Father in me ... [KJV]
... εγω εν τω πατρι και ο πατηρ εν εμοι... [TR, undisputed]
Jesus repeats this in John 14:11.
This cannot be a matter of physical humanity, since 'God is spirit', John 4:24. To be 'in' God cannot be a matter of manifested human nature but must be a matter spirit (see later in Ephesians).
Thus this is a matter of the person in a spiritual way. And if the 'Father' is in view than it must be a matter of 'I' as Son of God, not 'I' as humanity. It is a matter of divine relationship, in spirit.
This must denote a divine relationship of Father and Son. And must denote an intimate union of Person in that one is 'in' the other and the other is 'in' the one.
So what does Jesus' use of the preposition εν (always, of course, with the dative) convey ?
With regard to the second part of Jesus' saying ('and ye in me and I in you') there is, perhaps, some indication of the force of the preposition εν in Paul's exposition in Ephesians 3, 4 and 5.
In 3:17 Paul speaks of 'Christ dwelling in your hearts by faith', and in 3:9 that such should 'know the love of Christ' and in 3:19 he says that these same persons 'might be filled with all the fulness of God'.
Then he goes on to say in 4:5 and 6 that 'One Spirit ... one Lord ... and one God and Father of all' is 'in you all'.
Moreover in 4:10 Paul says that 'he ... that ascended up far above the heavens' did so 'that he might fill all'. (I notice that 'things' in the KJV is not there in the original : it is 'all'.)
And finally, 5:18, Paul urges these same persons that they should be 'filled with the Spirit'.
Is it the case that Jesus' use of the preposition εν in John 14:20 has the force of suggesting the same indwelling as Paul speaks of - an indwelling of all the 'fulness' of God ?
Does the force of εν (+ dative) suggest a fulsome indwelling ?