A.T. Robertson Commentary Romans 15:26

"For it hath been the good pleasure of Macedonia and Achaia to make a certain contribution for the poor among the saints that are at Jerusalem." — Romans 15:26 (ASV)

For it hath been the good pleasure of Macedonia and Achaia (ηυδοκησαν γαρ Μακεδονια κα Αχαια). "For Macedonia and Achaia took pleasure." The use of ηυδοκησαν (first aorist active indicative of ευδοκεω) shows that it was voluntary (2 Corinthians 8:4). Paul does not here mention Asia and Galatia.

A certain contribution (κοινωνιαν τινα). Put thus because it was unknown to the Romans. For this sense of κοινωνιαν, see 2 Corinthians 8:4; 9:13.

For the poor among the saints (εις τους πτωχους των αγιων). Partitive genitive. Not all there were poor, but Ac 4:32-5:11; 6:1-6; 11:29f.; Galatians 2:10 prove that many were.