In Acts 2, when David wrote 'thou wilt not leave my soul in hell,' was he talking about himself or about Christ?
David was not speaking of himself. Being a prophet, he foresaw and spoke of the resurrection of Christ. Peter explains that David is dead and buried, so the psalm's promise that God would not leave His soul in hell or let His Holy One see corruption refers to Christ, not David.
Les teaches that David is not referring to himself in the psalm. David is quoting Christ, had He been in those situations. Peter then argues that David is both dead and buried, and his sepulcher remains to that day, so David could not be the one death could not hold. Because David was a prophet, and God had sworn with an oath that He would raise up Christ from the fruit of his loins to sit on his throne, David foresaw and spoke of the resurrection of Christ. The King they crucified was raised by God and can still be their King.