What is the purpose of this Sunday's collection at First Purchase African Methodist Episcopal Church in To Kill a Mockingbird?

Calpurnia decides to take Jem and Scout to the First
Purchase AME Church because Atticus was out of town, and he had not given Cal any
specific instructions about going to church. Cal was worried that if she allowed the
children to go alone, they would get in trouble again, just as they had when they tied
Eunice Ann Simpson to a chair in the furnace room. So, Cal made sure the kids were
spruced up, and she took them to her church. On this Sunday, Reverend Sykes announced to
the congregation that

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"The collection taken up today and for the next
three Sundays will go to Helen--(Tom Robinson's) wife, to help her out at
home."