What is the importance of the cross Marion requests to be placed at the head of his grave in the novel, The Violent Bear It Away?

A Cross is requested by Marion to be placed at the head of his grave in accordance with Christian custom. The Cross will be a part of Marion’s overall Christian burial, which Tarwater refuses to complete at the insistence of the voice. The voice encourages Tarwater to dispense with the Cross, for it will do nothing but rot by Judgment Day. In a sense, this becomes metaphorical for the actions of the Devil, who seeks to undermine the efforts of Christ.