The gentile Christians were returning the favor (Rom 15:27)

“They were pleased

To do this.

Indeed

They owe it to them.

If the gentiles

Have come to share

In their spiritual blessings,

They ought also

To be of service to them

In material things.”

ὐδόκησαν γάρ, καὶ ὀφειλέται εἰσὶν αὐτῶν· εἰ γὰρ τοῖς πνευματικοῖς αὐτῶν ἐκοινώνησαν τὰ ἔθνη, ὀφείλουσιν καὶ ἐν τοῖς σαρκικοῖς λειτουργῆσαι αὐτοῖς.

Paul said that these Macedonians and Achaia people were pleased (ὐδόκησαν γάρ) to do this.  Indeed, Paul said that they owed it to them (καὶ ὀφειλέται εἰσὶν αὐτῶν).  If the gentiles (τὰ ἔθνη) have come to share (ἐκοινώνησαν) in their spiritual blessings (εἰ γὰρ τοῖς πνευματικοῖς αὐτῶν), they ought (ὀφείλουσιν) also to be of service (λειτουργῆσαι αὐτοῖς) to them in material things (καὶ ἐν τοῖς σαρκικοῖς).  Paul then explained that these Christian Macedonians and people from Achaia were happy to contribute to the Jewish Christians in Jerusalem.  Paul even implied that they owed it to them as debtors.  They had come to share in the spiritual blessings from these Jewish Christians.  Now they would provide some material or fleshy materials as a service to these poor Jewish Christians in Jerusalem.  They were only repaying a spiritual favor with a material reward.  Do you contribute to the well-being of other Christians?