What is the significance of Steinbeck's phrase 'George's voice wastaking on the tone of confession' when George tells Slim how he once encouraged Lennie to jump into the Sacramento River?

George feels self-conscious about what he did to Lennie when they were younger. Slim is a Christ-figure in the novel and George likes telling Slim of his past. It is almost as if George is asking forgiveness from Slim for his past wrong doings.