Some will affirm that the apostles literally received the Holy Spirit at that moment. However, there are at least three arguments against this notion:
Jesus continued - "If you forgive the sins of any, they are forgiven them; if you retain the sins of any, they are retained" (John 20:23). Once they actually received the baptism of the Holy Spirit, they would be fully qualified for their ultimate mission of forgiving sins. It must be understood, of course, that in the absolute sense only deity can actually forgive or retain sins. However, since the gospel is God's power to save (cf. Rom. 1:16), and the act of preaching makes it available to others, there is a sense in which proclaimers of the gospel do forgive or retain sins (based on the response of the sinner to the divine message; cf. Matt. 16:19).
John goes on to tell us that Thomas, also known as the "Twin," was not with the other apostles when Jesus appeared to them. It is unknown as to why he was absent. However, whatever the reason, his absence caused him to miss sharing in the blessings (at least temporarily) that the Lord had made available to the others who were present. Dear listeners, those today who neglect the assembly deprive themselves of many spiritual blessings also!
Although the other disciples affirmed that they had seen the Lord, Thomas declared - "Unless I see in His hands the print of the nails, and put my finger into the print of the nails, and put my hand into His side, I will not believe" (John 20:25). Thomas didn't doubt that the others had seen and talked with someone, but the question was: "Who?" They said that it was Jesus, and Thomas, believing this to be impossible, thought that it must have been someone else whom they mistakenly identified as Jesus. However, he would not be deceived; he would thoroughly examine the wounds since they would identify whether or not this person really was the Lord!
Let it be noted that some degree of inquiry is proper, and it is not out of order for a person to demand reasonable proof for any proposition he is asked to accept. One should not be overly critical of Thomas in this regard for the other apostles did not accept the testimony of the women or the two disciples at first. Nearly all of them shared a certain skepticism until they saw the Lord with their own eyes.