In Acts 15 the apostles and elders met at Jerusalem to resolve a dispute over whether circumcision is a requirement for salvation.  Of course, Jewish converts to Christianity were circumcised, so this dispute only related to Gentile converts to Christianity.  The apostles and elders concluded that circumcision should not be required of the Gentile converts but rather that they should abstain from four things: things polluted by idols, sexual immorality, things strangled, and blood.

Act 15:20  but that we write to them to abstain from things polluted by idols, from sexual immorality, from things strangled, and from blood.

Act 15:29  that you abstain from things offered to idols, from blood, from things strangled, and from sexual immorality. If you keep yourselves from these, you will do well. Farewell.

Act 21:25  But concerning the Gentiles who believe, we have written and decided that they should observe no such thing, except that they should keep themselves from things offered to idols, from blood, from things strangled, and from sexual immorality.”

To the modern reader these four things seem strange and somewhat arbitrary.  To understand the decision, we need to look at the historical background and scriptural context.

The start of the problem was how certain Jewish converts viewed gentile converts. 

Act 15:1  And certain men came down from Judea and taught the brethren, “Unless you are circumcised according to the custom of Moses, you cannot be saved.”

Some Jewish converts viewed circumcision as a matter of salvation and insisted that gentile converts should be circumcised.

Act 15:2  Therefore, when Paul and Barnabas had no small dissension and dispute with them, they determined that Paul and Barnabas and certain others of them should go up to Jerusalem, to the apostles and elders, about this question.

The only way to resolve the issue was to take the matter to the apostles and elders in Jerusalem.

Act 15:3  So, being sent on their way by the church, they passed through Phoenicia and Samaria, describing the conversion of the Gentiles; and they caused great joy to all the brethren.
Act 15:4  And when they had come to Jerusalem, they were received by the church and the apostles and the elders; and they reported all things that God had done with them.

Paul and Barnabas were well received by the church at Jerusalem.

Act 15:5  But some of the sect of the Pharisees who believed rose up, saying, “It is necessary to circumcise them, and to command them to keep the law of Moses.”

Some of the Pharisees who had converted to Christianity pushed for the gentiles to be circumcised.

Act 15:6  Now the apostles and elders [presbuteros] came together to consider this matter.

Note that is was the apostles and elders who were involved in the discussion and decision.  The word “elders” is translated from the Greek presbuteros which simply means those who are older in age.

Act 15:7  And when there had been much dispute, Peter rose up and said to them: “Men and brethren, you know that a good while ago God chose among us, that by my mouth the Gentiles should hear the word of the gospel and believe.
Act 15:8  So God, who knows the heart, acknowledged them by giving them the Holy Spirit, just as He did to us,
Act 15:9  and made no distinction between us and them, purifying their hearts by faith.

Peter reminded everyone that God had already given His Spirit to the gentiles.  For example, the uncircumcised Cornelius and his household received the Holy Spirit, Acts 10:1 through to 11:18.  So the question of whether gentiles needed to be circumcised had already been answered by God.

Act 15:10  Now therefore, why do you test God by putting a yoke on the neck of the disciples which neither our fathers nor we were able to bear?

Because God had given His Spirit to the gentiles Peter concluded that the gentiles should not be burdened with requirements the Israelite ancestors could not bear. 

Act 15:11  But we believe that through the grace of the Lord Jesus Christ we shall be saved in the same manner as they.”

God was now offering salvation to all through Jesus Christ.

Act 15:12  Then all the multitude kept silent and listened to Barnabas and Paul declaring how many miracles and wonders God had worked through them among the Gentiles.

Barnabas and Paul offered more proof that God was working with the gentiles through the miracles God performed among them.  James then spoke.

Act 15:13  And after they had become silent, James answered, saying, “Men and brethren, listen to me:
Act 15:14  Simon has declared how God at the first visited the Gentiles to take out of them a people for His name.
Act 15:15  And with this the words of the prophets agree, just as it is written:
Act 15:16  ‘AFTER THIS I WILL RETURN AND WILL REBUILD THE TABERNACLE OF DAVID, WHICH HAS FALLEN DOWN; I WILL REBUILD ITS RUINS, AND I WILL SET IT UP;
Act 15:17  SO THAT THE REST OF MANKIND MAY SEEK THE LORD, EVEN ALL THE GENTILES WHO ARE CALLED BY MY NAME, SAYS THE LORD WHO DOES ALL THESE THINGS.’
Act 15:18  “Known to God from eternity are all His works.

Verses 16 and 17 are quoting from

Amo 9:11  “On that day I will raise up The tabernacle of David, which has fallen down, And repair its damages; I will raise up its ruins, And rebuild it as in the days of old;
Amo 9:12  That they may possess the remnant of Edom,  And all the Gentiles who are called by My name,” Says the LORD who does this thing.

James then added to what had been said already by declaring that the prophecies about God working with the gentiles was being fulfilled now through the miracles God was working with the gentiles.  And with that James listed the restrictions they placed on the gentiles.

Act 15:19  Therefore I judge that we should not trouble those from among the Gentiles who are turning to God,
Act 15:20  but that we write to them to abstain from things polluted by idols, from sexual immorality, from things strangled, and from blood.

Each of the four restrictions violated specific biblical commands

Abstain from things polluted by idols

Exo 20:23  You shall not make anything to be with Me—gods of silver or gods of gold you shall not make for yourselves.

Abstain from sexual immorality

Exo 20:14  “You shall not commit adultery.

Abstain from things strangled and from blood

Deu 15:23  Only you shall not eat its blood; you shall pour it on the ground like water.

If an animal is strangled, then its blood is not released but stays in the animal carcass.  Therefore, in eating a strangled animal there is great risk in eating blood.

Clearly more things were required of gentile converts that just these four things.  For example, James wrote later that we should “be doers of the word”, “continue in the perfect law of liberty”, “bridle our tongue”, and “and keep oneself unspotted from the world”, James 1:22-27.  So why did James list only these four restrictions?  James gives the answer in the next verse.

Act 15:21  For Moses has had throughout many generations those who preach him in every city, being read in the synagogues every Sabbath.”

The apostles wanted to ensure that every new gentile convert would have access to the Scriptures.  The words of Moses (the first five books of the Old Testament) were read every Sabbath in the synagogues.  In that day only the very wealthy could afford any their own copies of the Old Testament, as scrolls were handwritten and enormously expensive.  The only access Christians had to the Old Testament was at the synagogues where it was read out loud every Sabbath.

By adhering to the four restrictions: “abstain from things polluted by idols, from sexual immorality, from things strangled, and from blood”, gentile converts would be allowed by the Jews to attend the synagogues.  Why was this important?  When the Church first began accepting gentile converts, it did not yet have the capacity to instruct them in the Scriptures in those cities having no Christian congregations.  The gentile converts could receive basic instruction in the Scriptures and God’s way of life by attending the regular synagogue services.  That allowed Paul and the other apostles to concentrate their efforts on explaining the role and mission of Jesus Christ and then move on to another city.