Sometimes apologists can spend a lot of time defending the resurrection. But what we tend to forget is that unless Jesus rose, he couldn’t have ascended. And is the ascension didn’t happen, these two events never happened. I am indebted to R.C Sproul for these two points:
First , because of the ascension, Jesus went up to His coronation. He did not go up simply to enter into His rest. He went up for His investiture service. He ascended to the throne, to the right hand of God, where He was given dominion, power, and authority over the whole earth. The Lamb who was slain became the Lion of Judah, who now reigns over the earth. Again, the church has failed to understand. Many still look at the kingdom of God as something in the unfulfilled future. But the kingdom has begun. Why? Because the King has been enthroned. When we recite the Apostles’ Creed, we affirm that Jesus “ascended into heaven and sitteth at the right hand of God the Father Almighty.” He now sits in the seat of authority at the right hand of the Father, acting, as it were, as the celestial Prime Minister. The New Testament gives Him the titles of King of Kings and Lord of Lords (1 Tim. 6: 15; Rev. 17: 14; 19: 16). Jesus is no longer a peripatetic rabbi, walking around Galilee and Judea. He is enthroned, and no monarch in this world can rule for a second apart from His authority. He brings kingdoms up and brings kingdoms down. He is accountable to no earthly ruler. Needless to say, the reign of our Lord is a tremendous benefit for those who love Him and follow Him. For this reason, it is clearly better for us that Jesus left than if He had stayed.
The Promise of the Spirit
Second, if Jesus had not ascended, he could of never sent the Holy Spirit. The word parakletos literally means “one called alongside.” In the ancient world, the parakletos was the family attorney. If a person was facing a difficult problem, he would summon the parakletos, and the parakletos would come alongside the person and help him through his problem. Jesus told the disciples they were going to have problems: “They will put you out of the synagogues; yes, the time is coming that whoever kills you will think that he offers God service” (John 16: 2). For this reason, He gave them the promise of the Holy Spirit, a Parakletos, to give them strength, to stand beside them in times of crisis so that they might prove faithful. This is why He told them, “Tarry in the city of Jerusalem until you are endued with power from on high” (Luke 24: 49). The last question the disciples asked Jesus before the ascension was this: “Lord, will You at this time restore the kingdom to Israel?” Jesus replied: “It is not for you to know times or seasons which the Father has put in His own authority. But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth” (Acts 1: 6– 8). So, one of the most important reasons for Jesus’ ascension was that Pentecost might take place, that the Father and the Son might pour out the Spirit on the church to strengthen it and empower it for its earthly mission.-see Sproul, R. C. The Work of Christ: What the Events of Jesus’ Life Mean for You (p. 188), Kindle Edition.
Also, see this current resource.