It was on that evening of Jesus’ resurrection from the dead when He appeared to His apostles that they were born again. Like the first man Adam who became alive as God breathed into his nostrils the breath of life, so did these come alive spiritually as Jesus breathed into them the Spirit of His resurrection life; Joh 20:22. They were the firstborn of the Firstborn from the dead, and like Adam they would become the spiritual progenitors of a new creation God was accomplishing through the death and resurrection of His only begotten Son, the Lord Jesus Christ. As the Father had sent Him, so was He now sending them with the same mission. As at His own baptism when the Holy Spirit descended and remained upon Him, in fifty days on Pentecost that same Spirit would fall upon them in power to mark the beginning of their own ministry to carry throughout the whole world what Jesus had begun, to establish God’s kingdom on earth as it is in heaven. Like Him, they would herald the favorable year of the Lord by preaching the gospel to the poor, proclaiming release (lit. forgiveness) to the captives, recovery of sight to the blind, and setting free (lit. extending forgiveness to) those who are downtrodden; see Luk 4:18-19.
It is in this regard that as He breathed into them His breath of resurrection life He also extended to them the same authority the Father had given Him, to herald the forgiveness of sins to those whose sins have been forgiven, while at the same time holding fast the sins of those whose sins have not been forgiven; see Joh 20:23 and note the perfect tense and the NAS text note. I.e., their authority was not to forgive sins according to their own whims in the way that degenerated into a source of worldly power and control that marked the Roman Church of the Middle Ages and led to the Protestant Reformation. Rather, their authority was the ability to proclaim forgiveness to those who on the basis of their faith in God demonstrate that their sins have in fact been forgiven by Him, while at the same time withholding the pronouncement of such forgiveness from those whose lives evidence no such faith. Such faith may be very nascent, and may in time fail to mature and prove stillborn. But through the Spirit of Jesus’ resurrection life breathed into them they would be able to discern even the most incipient faith, and on that basis proclaim the heart of the Father, that He has forgiven their sins, that they should have no doubt about His good will to continue to extend His mercy to them as they continue in His grace to come to complete at-one-ment with Him. What examples has Scripture recorded for us that illustrate the sort of evidence that demonstrates that faith by which Jesus’ followers may know, and proclaim, that God has forgiven a person’s sins? See Luk 7:41-50, 19:8-10, Act 8:27-28,36-37, 16:14-15,29-34; see also Luk 5:19-20 and think: what did the faith of the man’s friends that Jesus “saw” indicate about his own faith? Although he was paralyzed and so was limited in anything he could do to demonstrate his own faith, would he have had friends with such faith or allowed them to do what they did if he didn’t have faith himself? Cf. Act 14:9, 1Co 12:10.
What example do we have in Scripture of how someone’s sins, having initially been forgiven, were later retained or held fast due to an iniquity that acted as an impediment to his at-one-ment with God? See Act 8:13,18-23. What sin is explicitly and repeatedly mentioned in Scripture that will cause our own sins to be retained and not forgiven? See Mat 6:12,14-15, 18:26-30,34-35, Luk 11:4. What example do we have of what it actually looked like in practice for someone’s sins to be retained by the authority of the church? See 1Co 5:1-5,9-13. How does this help us to better understand the power of binding and loosing that Jesus conferred upon His disciples in Mat 18:18? See Mat 18:15-18 and the grammatical construction in Mat 18:18 that is similar to that found in John 20:23. What does the context of Mat 18:16,17,19 indicate about the safeguard built into the authority to forgive sins to help prevent the abuse of such authority by the whims of any individual? What do these things then teach us about the authority of the local and even greater church to establish standards of righteousness as a basis to adjudicate matters of church discipline? Cf. Act 15:22-29, 1Co 6:1-6. While the authority to forgive sins expressed in Mat 18:15-20 and Joh 20:23 extends to the Church in general, especially regarding more local and interpersonal matters, what similar authority did Jesus entrust specifically to Peter in Mat 16:19 with the keys to the kingdom of heaven on a much larger scale? See Act 2:14,37-39, 8:14-15,18-20,25, 10:1-2,5,43-45,47 for how Peter initially opened the door of salvation through the forgiveness of sins not just to the Jews, but also to the Samaritans and Gentiles. Cf. Act 16:7.