Then the apostles and the elders, together with the whole church, resolved to select men from among their number and send them to Antioch with Paul and Barnabas. They chose Judas called Barsabbas, and Silas, [both] leading men among the brethren, and sent them. With [them they sent] the following letter: The brethren, both the apostles and the elders, to the brethren who are of the Gentiles in Antioch and Syria and Cilicia, greetings: As we have heard that some persons from our number have disturbed you with their teaching, unsettling your minds and throwing you into confusion, although we gave them no express orders or instructions [on the points in question], It has been resolved by us in assembly to select men and send them [as messengers] to you with our beloved Barnabas and Paul, Men who have hazarded their lives for the sake of our Lord Jesus Christ. So we have sent Judas and Silas, who themselves will bring you the same message by word of mouth. For it has seemed good to the Holy Spirit and to us not to lay upon you any greater burden than these indispensable requirements: That you abstain from what has been sacrificed to idols and from [tasting] blood and from [eating the meat of animals] that have been strangled and from sexual impurity. If you keep yourselves from these things, you will do well. Farewell [be strong]! So when [the messengers] were sent off, they went down to Antioch; and having assembled the congregation, they delivered the letter. And when they read it, the people rejoiced at the consolation and encouragement [it brought them]. And Judas and Silas, who were themselves prophets (inspired interpreters of the will and purposes of God), urged and warned and consoled and encouraged the brethren with many words and strengthened them. And after spending some time there, they were sent back by the brethren with [the greeting] peace to those who had sent them. However, Silas decided to stay on there. But Paul and Barnabas remained in Antioch and with many others also continued teaching and proclaiming the good news, the Word of the Lord [concerning the attainment through Christ of eternal salvation in God's kingdom]. (Acts 15:22-35 AMP)

After James, the pastor in Jerusalem, had made his decision, delegates were chosen to be sent to Antioch to report, by official letter, this decree.
As we recall the setting, Antioch of Syria was the place where the men of Judea had made their claim that the Gentiles were to be circumcised in order to be saved. It was necessary, then, to send a delegation to Antioch to address the issue on behalf of the authority vested in the overseer of the churches, James. He was the overseer of the entire church body. After hearing the counsel of the men under his charge, he made a decision. We see a very significant point here. Peter, Paul, the rest of the apostles, Barnabas, and all the other believers were in submission to their Pastor. This is something that has been lost in our time. Pastors are looked at as hired employees that do the preaching, teaching, visiting, baptizing, marrying, burying, and other "ministerial" duties. This is, most certainly, honorable service. However, there is an anointing and calling from God that supersedes these things. The pastor is an overseer (see I Thessalonians 5:12-13; I Timothy 3:1-7; Titus 1:5-9; Hebrews 13:7,17; I Peter 5:1-4). The word "Pastor" means shepherd. He is one who leads. Sheep don't lead sheep. Shepherds lead sheep. There was no denominational handbook to refer to as an official declaration of doctrine. The Jerusalem church, under the godly leadership of James, Jesus brother, was in complete agreement with their Pastor. They accepted his decision and determined to send witnesses of this to Antioch to verify it in person and letter. The church was in its infancy and had come out of the roots of Judaism. Jesus was the center of their message. He was the New Covenant Truth. God's grace was the revelation of the church. This was hard for some to swallow since they had been wrapped up in such tradition and liturgy in their years of devotion to Judaism (Jewish faith and practice). Great anointing, wisdom, knowledge, and boldness was needed to preach, teach, and establish the foundation of the New Testament church. No wonder God took Paul into the third heaven in 2 Corinthians 12. He had to receive, without question, the absolute truth of the gospel of the grace of Jesus Christ and to understand the hardships that would befall him and others as they would be sent to declare it. This is why he was given the thorn in the flesh in 2 Corinthians 12 as well. This thorn would keep him from getting too haughty in the depth of his God given revelation.
The church sent, to Antioch, Judas (Barsabbas), and Silas to accompany Paul and Barnabas as they relayed the declaration to the church. Antioch already knew Paul and Barnabas, but, in order to give further verification of their proclamation, they sent these two brothers in Christ along with them. Judas and Silas were godly, seasoned ministers of Christ. This gave further credence to the letter. After the church heard the reading of the letter, they rejoiced. They were relieved and encouraged. Judas and Silas spoke to the congregation to exhort them in the truth. Following this, they were sent back to Jerusalem. Judas returned, but Silas stayed.