Having done the Lord's will and made up the number of Apostles the Disciples were settled. Jesus had told them to "wait for the promise of the Father".

Acts 2'1-4:

"They were all with one accord in one place.

And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting.

Then there appeared to them divided tongues, as of fire, and one sat upon each of them.

And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance".

The Lord had told them they would receive the Holy Spirit. It was the Spirit who inspired him to stand up and who gave him the ability to preach and unlock the door that stood in front of him.

Here are excerpts from the report:

Acts 2:

5. "And there were dwelling in Jerusalem Jews, devout men, from every nation under heaven".

14."... Peter, standing up with the eleven, raised his voice and said to them, 'Men of Judea and all who dwell in Jerusalem, let this be known to you, and heed my words'".

36-40. “Therefore, let all the house of Israel know assuredly that God has made this Jesus, whom you crucified, both Lord and Christ.”

Now when they heard this, they were cut to the heart, and said to Peter and the rest of the apostles, 'Men and brethren, what shall we do?'

Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit.

For the promise is to you and to your children, and to all who are afar off, as many as the Lord our God will call.”

And with many other words he testified and exhorted them, saying, “Be saved from this perverse generation".

By the time he had finished, the key had been fully turned and the result was that -

40. "Those who gladly received his word were immersed and that day about three thousand souls were added to them".