Aruch HaShulchan, The Laws of Tzedakah, 248:4

The Tur and the Shulchan Aruch in the introductory paragraph in chapter 248 wrote that every person is obligated to give, even the poor, etc., and that whoever gives less than what is suitable for them to give, the court can force and even punish that person for their disobedience until they give what the court has assessed them to give. The court can go into that person’s possessions in their presence and take what is suitable for that person to give - until there are the Tur and Shulchan Aruch’s words. There are those who wrote that this does not refer to a poor person....This teaches us that the tzedakah the poor gives should be accepted. Lest you erroneously think that after the poor person gives a third of a shekel no more can be accepted, this teaches us that his is not so. It also says that a poor person cannot be obligated to give because they are exempt from the commandment of tzedakah every year after they have given their obligatory third of a shekel...[Translation by Rabbi Bruce Elder. Edited for gender neutrality]