Paul writes to the Corinthians and encourages them to donate their riches (or a portion of them) to the poor. Even those who don’t have much can give something. Those who give will see that; “…their deep poverty abounded unto the riches of their liberality.” (2 Corinthians 8:2)
Paul puts his name on the line for Titus (who would be handling their money). Paul explains that even Christ was poor, but through His giving He became rich in spirit.