It was revealed to them that they were not serving themselves but you, when they spoke of the things that have now been told you by those who have preached the gospel to you by the Holy Spirit sent from heaven. Even angels long to look into these things.
NIV
It was then disclosed to them that the services they were rendering were not meant for themselves and their period of time, but for you. [It is these very] things which have now already been made known plainly to you by those who preached the good news (the Gospel) to you by the [same] Holy Spirit sent from heaven. Into these things [the very] angels long to look!
AMP
Unto whom it was revealed, that not unto themselves, but unto us they did minister the things, which are now reported unto you by them that have preached the gospel unto you with the Holy Ghost sent down from heaven; which things the angels desire to look into.
KJV
Trying to find out the time and circumstances to which the Spirit of Christ in them was pointing when he predicted the sufferings of Christ and the glories that would follow.
NIV
They sought [to find out] to whom or when this was to come which the Spirit of Christ working within them was indicating when He predicted the sufferings of Christ and the glories that should follow [them].
AMP
Searching what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow.
KJV