Christ told His disciples that if He did not go away, the Holy Spirit would not come (John 16:7). When the Holy Spirit came, Jesus also came in the Holy Spirit (John 14:17-18). He was transfigured from the body into the Spirit (1 Cor. 15:45). So, after His resurrection, He came back in the Spirit in a resurrected body (John 20:19). In the Spirit He breathed on the disciples saying, "Receive ye the Holy Spirit" (John 20:22). Thus, by the resurrection, He brought Himself as the Spirit of life into the disciples.
Many people today think that the Holy Spirit never came before Pentecost. But in the evening of the day of resurrection, Christ came and breathed on the disciples, saying, "Receive ye the Holy Spirit." That means the Holy Spirit came into the disciples that very night. On the day of resurrection, early in the morning, the Lord went to the Father for a short while (John 20:17). Then, in the evening, He came down to the disciples with the Spirit of life.
This is confirmed by another instance. Before Pentecost the one hundred and twenty disciples prayed together for ten days in harmony (Acts 1:13-15)! Do you believe that without the Holy Spirit of life within them they could be in such accord for ten days? Try it. I’m afraid you will soon be quarreling with others. We remember how the disciples contended with one another before the Lord died (Luke 22:24). Everyone wanted to be the greatest. But after the resurrection, those poor fishermen of Galilee boldly left their country and went to stay in Jerusalem, though the place was filled with threatening against them (John 20:19). Not only did they go and abide together there, but they also prayed in one accord for ten days. This was not something that came from themselves; it was something of the Spirit of life. They had the Holy Spirit of life within them. Peter could even stand up and give a message from the Scriptures showing the fulfillment of prophecy (Acts 1:15-20). That came from the Spirit of truth. Thus we see that the disciples received the Spirit of life before Pentecost. They became living members, though not yet formed into one Body. Therefore, they waited for the power from on high (Luke 24:49), the baptism in the Holy Spirit (Acts 1:5, 8) through which they would be formed into a living Body.
The Lord’s children today confuse these things. Some people say the baptism of the Holy Spirit is the second blessing. Others say it is for sanctification. This is nothing but confusion. The baptism in the Holy Spirit is for the formation of the Body (1 Cor. 12:13). The resurrection of Christ is for the regeneration of living members for the Body, while the ascension of Christ brings down the Holy Spirit of power so that we may be baptized into one Body.
(The Four Major Steps of Christ, Chapter 4, by Witness Lee)