To bring the “whole” (literally, all things; not some things or Christian things only) “in Christ” as the verses below “plainly” declare:

(note that this takes place in the ‘dispensation’ of “times” {plural} proving again that not all are saved [gathered in Christ] at the same time):

“having made known to us the secret of His will, according to His good pleasure, that He purposed in Himself, 

in regard to the dispensation of the fullness of the times, to bring into one the whole (all things)in Christ, both the things in the heavens, and the things upon the earth — in Him;” (Ephesians 1:9 – 10)

“fullness” of the “times” tells us “literally” that all these will be fulfilled in the “ages framed by the word of God” (as declared by the author of Hebrews) in Hebrews 11:3 as follows:

“by faith we understand the ages to have been framed (prepared) by the word of God, in regard to the things seen not having come out of things appearing;” (Hebrews 11:3)

This agrees with apostle Paul’s declaration that as an apostle who speaks the “truth” about/in Christ, Paul says this “truthful” declaration (which differentiates truth versus false doctrines) in the verses below where Christ’s “ransom” (paid at the Cross) will be “testified” (its testimony come to pass) in due “times” (plural; indicating at different period of times, this will be true) for “all” (the whole; not some or Christian things only):

“Who (Lord Jesus) did give Himself a ransom for all (not some or Christians only) the testimony in its own times — in regard to which I was set a preacher and apostle — truth I say in Christ, I do not lie — a teacher of nations, in faith and truth.” (1 Timothy 2:6 – 7)