What should believers maintain about their salvation?
Believers should maintain that salvation is by grace through faith, plus nothing. They are not under Law but under grace, and must not be drawn into any works religion. Salvation comes by faith, not by keeping the Law, and nothing can be added to it.
Les teaches that the theme of Galatians is that we are not under Law but under grace. He asks how we come under grace and out from under the Law, and answers: by faith, plus nothing. He warns believers not to be suckered into coming under some kind of a works religion. The key point he wants remembered is to maintain the fact that we are saved by grace through faith, plus nothing.