Jesus instructed His apostles to wait in a specific place--that is, Jerusalem. It was there they would receive "the Promise of the Father" that Jesus had spoken of previously. In essence, this was the reception of the Holy Spirit for purposes of divine guidance. It is important that we carefully note to whom Jesus was speaking. To whom did Jesus promise divine guidance?
On the evening of His betrayal, Jesus "sat down with the twelve" (Matt. 26:20). The context shows that the events of John 13-18 also happened on the evening of His betrayal. Thus, Jesus' lengthy portions of continued dialogue found in John 13ff were directed to the apostles and matters addressed therein should not be automatically understood to be applicable to all disciples in general--either then or now. Carefully consider the following statements from Christ:
In Acts 1:5, Jesus speaks of John's baptism (cf. Mark 1:4; Luke 3:3; and our lesson from 03/16/05). Our Lord then affirms - "but you shall be baptized with the Holy Spirit not many days from now." The primary audience of His words on this occasion was the same as it was on the night of His betrayal--that is, His apostles. Such is understood from the reasoning explained above as well as the immediate context of Acts 1. It was the apostles whom Jesus had chosen (cf. 1:2), and to whom He had presented Himself alive after His resurrection (cf. 1:3), and to whom He had commanded to remain in Jerusalem for the time being (cf. 1:4), that He was now speaking to! More proof of this truth will be shown when we consider Acts 2.
So, the apostles of Christ would soon be "baptized with the Holy Spirit" in Jerusalem. More specifically, this would occur ten days after Jesus' ascension. We know this to be the case since the promise was fulfilled on Pentecost in Acts 2. Pentecost was always 50 days after the Passover Sabbath. Jesus was raised the day after this Sabbath and showed Himself to the apostles over forty days. Thus, after His ascension, there were ten days remaining until Pentecost. This baptism (or overwhelming measure of the Spirit's power) would enable them to infallibly proclaim the message of God. It was the final qualification needed to equip them to fulfill the Great Commission (cf. Matt. 28:19,20). Without divine guidance, it should be obvious as to why they had been forbidden previously from preaching Jesus as the Christ (e.g., Matt. 16:20). Their crude conceptions of the Messiahship, their erroneous beliefs regarding the nature of the expected kingdom, their misunderstanding of much that He had taught them, and their imperfect remembrance of that which they had understood, rendered them incapable of presenting His claims truthfully to the world, and certainly not infallibly, without the guidance of the Spirit of truth.