Ephesians 4:8
Wherefore he saith, When he ascended up on high, he led captivity captive, and gave gifts unto men.

this is direct quote from 68:18.

the first thing here is eliminate what captivity is not. It is not the saved in Hades. They are nowhere else in any way described as being captives. In fact, inspiration tells us the truth will set us free. So what's left?

The lost in Hades could be represented here but I don't think that is what is in mind here.

I think the captivity here is the bondage of sin which captivated mankind until Jesus came and offered Himself as a sacrifice in man's place. Jesus Christ captured the captivity of sin by His sacrifice.

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"My little children, let us not love in word, neither in tongue; but in deed and in truth. And hereby we know that we are of the truth, and shall assure our hearts before him." 1 John 3:18-19

The church of Christ at Granby