Jesus granted Authority to the Apostles to forgive or retain sin.
“ What you bind on earth, shall be/ will be bound in heaven “ KJV / NKJV.
Jesus gave this great gift to the Apostles breathing The Holy Spirit on them.
What they declare on earth, Heaven will equally hold to.
“Father who knowest the hearts of all grant upon this Thy servant whom Thou hast chosen for the episcopate to feed Thy holy flock and serve as Thine high priest, that he may minister blamelessly by night and day, that he may unceasingly behold and appropriate Thy countenance and offer to Thee the gifts of Thy holy Church. And that by the high priestly Spirit he may have authority to forgive sins…” Hippolytus, Apostolic Tradition, 3 (A.D. 215).
We see this power of Christ is given to mere men through The Holy Spirit.
“For if any one will consider how great a thing it is for one, being a man, and compassed with flesh and blood, to be enabled to draw nigh to that blessed and pure nature, he will then clearly see what great honor the grace of the Spirit has vouchsafed to priests; since by their agency these rites are celebrated, and others nowise inferior to these both in respect of our dignity and our salvation. For they who inhabit the earth and make their abode there are entrusted with the administration of things which are in Heaven, and have received an authority which God has not given to angels or archangels. For it has not been said to them, ‘Whatsoever ye shall bind on earth shall be bound in Heaven, and whatsoever ye shall loose on earth shall be loosed in Heaven.’ They who rule on earth have indeed authority to bind, but only the body: whereas this binding lays hold of the soul and penetrates the heavens; and what priests do here below God ratifies above, and the Master confirms the sentence of his servants. For indeed what is it but all manner of heavenly authority which He has given them when He says, ‘Whose sins ye remit they are remitted, and whose sins ye retain they are retained?’ What authority could be greater than this? ‘The Father hath committed all judgment to the Son?’ But I see it all put into the hands of these men by the Son.” John Chrysostom, The Priesthood, 3:5 (A.D. 387).
It truly is an awesome thing.