Where does it say we take on the human spirit of our Lord Christ Jesus? Our human spirit is then indwelt by God the Holy Spirit. Our spirit is in our human body which becomes His temple or dwelling place which He has provided.
His human spirit is unique to Him, but we are all of one body, obedient to His Will.
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I posted one of the verses which state that we take on immortality when we “take on” Christ. If you have a problem with that then either post verses which contradict that or just learn to live with the realization that only those who accept Christ will live forever. Those who don’t will be destroyed in the Lake of Fire (second death-Revelation 20:14).