When was the plan of salvation established?
The plan of salvation was established in eternity past, before anything was ever created. The triune God agreed on creation and mankind, knowing mankind would sin, and set up the plan whereby the Son would come down, die, and be raised from the dead. This was God's eternal purpose.
Les explains that Paul is writing to Timothy, but the truth applies to every believer. Salvation is not according to our works; God called us according to His own purpose. Les points out that back in Acts, Peter makes it evident that before anything was ever created, the triune God had a meeting in eternity past. Not that they had to sit around and debate, but the Trinity got together and agreed on creation, on mankind, knowing that he would sin, and they set up the plan of salvation. Out of that plan, the Son would come down, die, and be raised from the dead. This is part of the eternal purpose God implemented before anything was ever created.