Most Bible scholars think Jesus's brother wrote the book.
James didn’t become a believer until after Jesus’ resurrection.
His letter was written to the Jewish Christians, challenging them, very strongly, even bluntly, to live out their faith in their everyday lives.
James 5:1-6
James 5:7-9
James 5:10-12
James 5:13-16
James 5:17-18
James 5:19-20