Albert Barnes on Romans 15:27

Of their spiritual things. Have received the gospel by the instrumentality of those who had been Jews; and were admitted now to the same privileges with them.

Carnal things. Things pertaining to the flesh; that is, to this life. On this ground the apostle puts the obligation to support the ministers of the gospel, 1Cor 9:11. It becomes a matter of debt where the hearer of the gospel receives, in spiritual blessings, far more than he confers by supporting the ministry. Every man who contributes his due proportion to support the gospel may receive far more, in return, in his own peace, edification, and in the order and happiness of his family, than his money could purchase in any other way. The gain is on his side, and the money is not lost. The minister is not a beggar; and that which is necessary to his support is not almsgiving. He has an equitable claim--as much as a physician, or a lawyer, or a teacher of youth has--on the necessaries and comforts of life.

(i) "duty is also to minister" 1Cor 9:11.