From the Hatydock Commentary:
Ver. 22. Receive ye the Holy Ghost. It was said, (John vii. 39.) that the Spirit was not yet given, because Jesus was not glorified. The sense must needs be, that the holy Spirit was not given in that solemn manner, nor with so large an effusion of spiritual gifts and graces, till the day of Pentecost, after Christ’s ascension: but the just, at all times, from the beginning of the world, were sanctified by the grace of the Holy Ghost, as no doubt the apostles were, before this time. Now at this present, he gave them the power of forgiving sins. (Witham) — Some say, that our Saviour did not then confer the Holy Ghost on his disciples, but only prepared them for the receiving of the Holy Ghost. But surely we may understand, that even then they received some portion of spiritual grace, the power, not indeed of raising the dead, and working other miracles, but of forgiving sins. (St. Chrysostom, hom. lxxxv. in Joan.) — St. Cyril of Alexandria, speaking of the remission of sins, promised in this text, asks, “How then, or why, did Christ impart to his disciples a power, which belongs to the divinity alone? It seemed good to him, that they, who had within themselves his divine Spirit, should likewise possess the power of forgiving sins, and of retaining such as they judged expedient; that Holy Spirit, according to his good pleasure, forgiving and retaining, through the ministry of men.” (In Joan. lib. xii. chap. 1.)
However, this cannot be read in isolation from:
Jesus Commissions the Disciples
14 Afterward he appeared to the eleven themselves as they sat at table; and he upbraided them for their unbelief and hardness of heart, because they had not believed those who saw him after he had risen. 15 And he said to them, “Go into all the world and preach the gospel to the whole creation. 16 He who believes and is baptized will be saved; but he who does not believe will be condemned. 17 And these signs will accompany those who believe: in my name they will cast out demons; they will speak in new tongues; 18 they will pick up serpents, and if they drink any deadly thing, it will not hurt them; they will lay their hands on the sick, and they will recover.”
Commissioning them is one thing which is done by the Holy Spirit. Empowering them at the Pentecost is quite another. The first is the bestowing of authority, while the second is the giving of the tools that they will need for ministry.