In Luke’s gospel we read
Luke 24:49-52. And behold, I am sending the promise of my Father upon you. But stay in the city until you are clothed with power from on high.” 50 Then he led them out as far as Bethany, and lifting up his hands he blessed them. 51 While he blessed them, he parted from them and was carried up into heaven. 52 And they worshiped him and returned to Jerusalem with great joy, 53 and were continually in the temple blessing God.
The apostles stayed in Jerusalem until the day of Pentecost when they received the Holy Spirit (Acts 2:1-4).
The time they waited is not explicitly given, but it is not hard to work out. We know Jesus died on the day of Passover (John 18:28), was resurrected three days later (Luke 24:7), and appeared to his disciples over a period of 40 days (Acts 1:3) which included the day he was resurrected. So he ascended to heaven 42 days after Passover.
Pentecost means “fiftieth day” and it was the 50th day of the Passover, or 49 days after Passover. It was called the “Feast of Weeks” in the Old Testament — the 49 day rule is given in Leviticus 23:15.
Therefore, there was a period of exactly 7 days from when Jesus went to heaven to when the apostles received the Holy Spirit on the day of Pentecost.