So here is a typical translation of Ephesians 3:19
Ephesians 3:19 – ESV
and to know the love of Christ that surpasses knowledge, that you may be filled with all the fullness of God.
When we checked the original language, Greek, the word “with” in the phrase “filled with all the fullness” is the conjunction “eis”. This word is usually translated as “into”.
So why is it translated as “with”. The metaphor is of being filled, and things are filled with other things. A glass is filled with water. A house is filled with music.
What sense is it to be filled “into” all the fullness? The conjunction “eis” is described in one reference: “if “en”is punctiliar, “eis” is the corresponding ‘linear’ word; where “en” = “in”, “eis” would rather = “into”. It may be added, as a rough-and-ready distinction between the meanings of “eis” and “pros”[toward], that “eis” tends to include the idea of entry…”
Bear with me – that bit of grammar from C. F. D. Moule’s “Idiom Book of the NT Greek” suggests that the picture should not be the fullness of God filling us like a cup, but of us plunging into the fullness of God. The prayer had previously sought that we be strengthened or enlarged in capacity to be the dwelling for Christ, now this idea is reversed to one where we move into the fullness of God. Or as we might say “take the plunge”.