Romans 15:27

Yea, it hath been their good pleasure; and their debtors they are. For if the Gentiles have been partakers of their spiritual things they owe it to them to minister unto them in carnal things.

Paul's collection for the poor, therefore, was initiated and executed, not solely out of respect to the needs of the poor Christians in Jerusalem, but also because of the debt of Gentile Christians who had received spiritual benefit from those same poor, thus establishing categorically the spiritual nature of the obligation to charity. The Gentiles needed to give, as much as the Christian poor of Jerusalem needed to receive. The filial bond uniting them as members of the one body in Christ was the basis of Paul's plea for the Gentiles to give, as well as the basis of the right of the Christian poor to receive. Without that filial bond, no obligation is here imposed by apostolic authority. It was not only the need of the poor that entitled them to receive, but their status as "brethren in Christ." This deduction is mandatory because, of the non-Christian poor in Jerusalem, it is not affirmed that the Gentile Christians "owed" them anything.