The phrase ‘You are no saint’ implies that the person the devil is talking to is not perfect or good. The response to this is that if the person is not perfect (a saint), they are likely a sinner. The speaker then goes on to say that since they are a sinner, Jesus Christ came into the world to save sinners. This means that since the person is a sinner and Jesus is the only one who can save them, they need to rely on God for salvation and trust that He will help. Relying on anyone or anything else will not work. Ultimately, the speaker has no other hope and must go to Jesus for salvation.