We read in the Book of Acts that the Christians at Antioch sent money to Jerusalem. Paul collected money as he traveled into Macedonia and into Greece proper. He refers to the one trip several times where, together with representatives of the Gentile churches, he went to Jerusalem to present this great offering. I suppose Paul thought of this as a testimony to the great unity of the Christian church. That is because here was a true, common brotherhood of those who had been born again and were brothers and sisters with Jesus Christ, showing a family concern for one another. So as Paul is writing to the Corinthians, he encourages them to give.