Those spoken of in this expression are identical with those described in the 16th verse as “dead in Christ.” For us Christ tasted death in all its meaning, and for us it is robbed of its sting, so that the death of a believer can be spoken of as “sleep.”
Rightly translated the preposition should be translated “through” not “in” Jesus. These have fallen asleep through Jesus.
Observe the perfection of Scripture; Jesus is the name which describes our Lord as man personally, thus believers are not spoken of exactly as in Jesus, but in Christ, “the anointed,” which is the title under which we come into relationship with Him in resurrection (Acts 2:3636Therefore let all the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ. (Acts 2:36)).