Acts 21: 10-11:
[A] prophet named Agabus came down from Judea [to Ptolemais]. And coming to us, he took Paul's belt and bound his own feet and hands and said, "Thus says the Holy Spirit, 'This is how the Jews at Jerusalem will bind the man who owns this belt and deliver him into the hands of the Gentiles.'"
vv. 17, 27-33:
[W]e had come to Jerusalem. . . . When the seven days were almost completed, the Jews from Asia, seeing him in the temple, stirred up the whole crowd and laid hands on him, crying out, "Men of Israel, help! This is the man who is teaching everyone everywhere against the people and the law and this place. Moreover, he even brought Greeks into the temple and has defiled this holy place." For they had previously seen Trophimus the Ephesian with him in the city, and they supposed that Paul had brought him into the temple. Then all the city was stirred up, and the people ran together. They seized Paul and dragged him out of the temple, and at once the gates were shut. And as they were seeking to kill him, word came to the tribune of the cohort that all Jerusalem was in confusion. He at once took soldiers and centurions and ran down to them. And when they saw the tribune and the soldiers, they stopped beating Paul. Then the tribune came up and arrested him and ordered him to be bound with two chains. He inquired who he was and what he had done.
Read the whole chapter to see the context in which this takes place.
Who does Agabus say with bind Paul? What does he say the Jews will do with Paul? He says that the Jews will bind Paul, and deliver him to the Gentiles. What does Luke say happened? The Jews were beating Paul to death, and the Romans came, took him (as opposed to received him) and bound him.
But Agabus is a Scripture affirmed prophet. The Deuteronomy 18 code for dealing with prophets who prophesy things that do not come to pass goes as follows:
"But the prophet who presumes to speak a word in my name that I have not commanded him to speak, or who speaks in the name of other gods, that same prophet shall die." And if you say in your heart, "How may we know the word that the LORD has not spoken?"—when a prophet speaks in the name of the LORD, if the word does not come to pass or come true, that is a word that the LORD has not spoken; the prophet has spoken it presumptuously. You need not be afraid of him. (vv. 20-22)
Surely if Luke thought that Agabus should be treated as Deuteronomy says to deal with a false prophet, Luke would not have called him a prophet.
I should point out that there are some who think that exactly what Agabus said came to pass. For example, John MacArthur said,
I can imagine Paul just saying, "Yes, what Agabus told me in Caesarea has come to pass." Go back. Chapter 21, verse 11, Agabus the prophet said - he came to town, he said, "By a picture that you're going to get down." What did he do? He took Paul's belt, bound his hands and feet. Said, "Thou said the Holy Spirit says. 'The Jews of Jerusalem are going to bind the man that owns the belt and deliver him to the hands of the Gentiles.'"
The prophecy comes to pass. The Jews have captured him. They've got him held, and they deliver him to the Gentiles, who chain him. The prophecy came true.
I think he's being creative in the way that he reads Agabus' prediction and Luke's record of the event in trying to harmonize them. I think it's wrong, but I should point out that there are those out there who, for whatever reason, don't read the passage the way that I think Luke meant it.
Now for implications: I don't know exactly what to infer from it. God is an infallible communicator, but He didn't promise that prophecy in the New Covenant age would be infallible. How to reconcile this:
God sends an infallible message to a prophet. That prophet must 1. see the vision, 2. interpret the vision, and 3. proclaim the interpretation. In any of those steps the prophecy could be misunderstood and have error added to that which was infallible. Take Agabus' example. Since it's in Scripture, Luke recorded it in a way that sufficiently represented Agabus' intentions of the prophecy since Scripture is always true. So maybe Agabus mistook Romans for Jews (i.e., he made a mistake at step 1), and thus thought that it would be the Jews who bind Paul instead of the Romans. It's a possibility. I don't know what really happened.
The major implication is that we need to use discernment when dealing with any revelation of God outside of His infallible, inerrant Word. For example, if we feel that God is leading us, we shouldn't be closed handed about it. We're fallible. We make mistakes. My fear in this is that we'll say that we feel called to do something, when it really isn't from God. We end up doing something stupid, the unbelieving world sees it, and then ends up using it as proof that our perfect God does not exist, when all it shows is that we're able to be stupid.