Behold, I send the Promise of My Father upon you; but tarry in the city of Jerusalem until you are endued with power from on high. (Luke 24:49)
The ability to receive and understand the power of God is through the Holy Spirit of God. The power of God is His Word. Therefore in essence, Jesus is saying that "The Promise of His Father" is the presence of the Holy Spirit, which is given that we might receive and understand the engrafted Word of God. Therefore be willing to tarry until you are endued with this power from on high. I have found in my three decades of walking with the Lord that these times come through the realm of patience. These times are usually during the hard times of life. When there is no time or room for me to get in the way, God seems to open the windows of heaven and poor out His Spirit in abundance. For this, it is worth waiting. When God makes a promise, He keeps it. However, it will not be according to our timetable, but His. And His timing is perfect.