In Acts 2, who asks 'what must we do' — the nation or individuals?
In Acts 2, it is the covenant nation of Israel that asks 'what must we do?' Peter is preaching to them as a nation, and they respond from the national standpoint. By contrast, Gentiles are dealt with as individuals, as seen in Acts 16 when the jailer asks 'what must I do to be saved?'
Les teaches that in Acts 2, Peter is preaching to the covenant nation of Israel, and the covenant nation, from the national standpoint, asks, 'what must we, the nation, do?' But God does not deal with Gentiles on covenants; He deals with them as individuals. Every individual must ask that same question, 'what must I do to be saved?' This is the difference Les highlights by comparing Israel's national response in Acts 2 with the individual Gentile jailer in Acts 16, who asked Paul and Silas, 'Sirs, what must I do to be saved?'