On one occasion, while he was eating with them, he gave them this command: "Do not leave Jerusalem, but wait for the gift my Father promised."
Then he opened their minds so they could understand the Scriptures. He told them, "This is what is written: The Christ will suffer and rise from the dead on the third day, and repentance and forgiveness of sins will be preached in his name to all nations, beginning at Jerusalem. You are witnesses of these things. I am going to send you what my Father has promised; but stay in the city until you have been clothed with power from on high."
Even though today is ascension Sunday, the ascension was to happen 40 days after the resurrection, so that puts it at about last Friday. At the moment we’re in a bit of a gap in the Christian calendar. After ascension, waiting for Pentecost.
In today’s text we hear an odd command. Wait. “Don’t leave Jerusalem, but wait for the gift my father had promised.” The disciples, too, have a gap to fill. Waiting for Pentecost. We know Pentecost was to come a bit more than a week later, but how would it have been just sitting and waiting for the outpouring of the spirit?
The disciples were Jews, and from the Old Testament the Jews didn’t have a very good track record of waiting. When Moses was receiving the 10 commandments, he told the elders and people of Israel to wait until he returned. While Moses was gone for 40 days, they wavered and faltered.
Then Moses set out with Joshua his aide, and Moses went up on the mountain of God. 14 He said to the elders, "Wait here for us until we come back to you. Aaron and Hur are with you, and anyone involved in a dispute can go to them."
When the people saw that Moses was so long in coming down from the mountain, they gathered around Aaron and said, "Come, make us gods who will go before us. As for this fellow Moses who brought us up out of Egypt, we don't know what has happened to him."
Then the LORD said to Moses, "Go down, because your people, whom you brought up out of Egypt, have become corrupt. They have been quick to turn away from what I commanded them and have made themselves an idol cast in the shape of a calf."
Then God got a little angry.
So back to the Disciples. They were given the instruction to wait for things to come. The gift God had promised is on the way. Wait. Earlier on, not 40 days beforehand, they also had been given a prediction of what was to come. Jesus mentioned many times that he was to be crucified, but on the third day he will rise again. Here is another gap where there seems to be nothing to do but sit and wait, but the disciples react badly. They huddle up in their rooms in fear. Fear of getting caught, fear that their world that has all fallen apart. Jesus had told them first in parables after clearing out the temple:
Jesus answered them, "Destroy this temple, and I will raise it again in three days."
Then throughout his ministry more plainly. After feeding the 4000 and healing the blind:
From that time on, Jesus began to explain to his disciples that he must go to Jerusalem and suffer many things at the hands of the elders, chief priests and teachers of the law, and that he must be killed and on the third day be raised to life.
And again after many more miracles and parables:
Now as Jesus was going up to Jerusalem, he took the twelve disciples aside and said to them, "We are going up to Jerusalem, and the Son of Man will be betrayed to the chief priests and the teachers of the law. They will condemn him to death and will turn him over to the Gentiles to be mocked and flogged and crucified. On the third day he will be raised to life!"
The time of waiting from Christ’s death to eventual resurrection should have been one of anticipation. The biggest miracle ever was close at hand! Yet they cowered.
In contrast, the disciples approach the Ascension and following days in a totally different manner. We read from the end of Luke:
When he had led them out to the vicinity of Bethany, he lifted up his hands and blessed them. While he was blessing them, he left them and was taken up into heaven. Then they worshiped him and returned to Jerusalem with great joy. And they stayed continually at the temple, praising God.
What a change. What a way to wait, praising God. The difference? 40 days. A long time. Jesus had spent 40 days proving himself to be the resurrected Christ. He appeared to the disciples, to Thomas, to the men on the road to Emmaus. He ate with them and talked with them. Still, we hear their faith was lacking:
Later Jesus appeared to the Eleven as they were eating; he rebuked them for their lack of faith and their stubborn refusal to believe those who had seen him after he had risen.
Disciples had lacking faith? Didn’t they gave up everything to follow Jesus? Martin Luther, in a sermon on ascension, explains the difference:
Martin Luther 
But let no one think that the apostles were altogether unbelieving; they believed what was written in the Law and the prophets, although their faith was not yet perfect. They believed that God created heaven and earth, and was the Maker of every creature. The Lord, however, shows what they lacked; they did not believe the resurrection of Christ from the dead. Although they believed the other things, they were still lacking in this. I hold that they believed that they had a gracious God. Yet this was not enough; they must believe also the resurrection of Christ. Christ’s words to them at the Last Supper: "You believe in God, believe also in me." John 14, 1.
What does it mean, then, to believe the resurrection of Christ? This thing which is so important that without it the disciples were called unbelieving and faithless? To believe the resurrection of Christ, is nothing else than to believe that we have a Mediator before God. Who is Christ, who makes us holy and acceptable to God the Father. For man's possessions, by birth and nature, are but sin and corruption, by which he brings down upon himself the wrath of God. But God is eternal righteousness and purity, and therefore, from his very nature, hates sin. Hence there is always enmity between God and the natural man. They cannot be harmony with one another.
For this cause, Christ became man and took upon himself our sins and also the wrath of the Father, and drowned them both in himself, thus reconciling us to God the Father. Without this faith, we are children of wrath, able to do no good work that is pleasing to God.
The disciples had faith in the God of Law, the God that talked to Moses calling the people of Israel corrupt. Jesus rebukes their lack of faith, but opens their minds to the Scriptures:
He said to them, "This is what I told you while I was still with you: Everything must be fulfilled that is written about me in the Law of Moses, the Prophets and the Psalms."
Then he opened their minds so they could understand the Scriptures. He told them, "This is what is written: The Christ will suffer and rise from the dead on the third day, and repentance and forgiveness of sins will be preached in his name to all nations, beginning at Jerusalem. You are witnesses of these things.”
The disciples, finally seeing the jigsaw puzzle complete before their eyes, are filled with joy! As Jesus ascends, they praise him. As they wait for Pentecost, they praise him!
So here we are today; in the lull between Ascension and Pentecost. We can look back at the past and learn from the disciples. And with the disciples, let us also praise the Lord for Christ has risen for you, for me, for everyone.
 Sermon for the Day of Christ’s Ascension; Mark 16:14-20 (2nd sermon) by Martin Luther; taken from his Church Postil, 1522.