Every sermon is a "salvation sermon"

Preaching is a means of grace to assist the saints to persevere. Perseverance is necessary for final salvation. Therefore, every sermon is a "salvation sermon"—not just because of its aim to convert sinners, but also in its aim to preserve the holy affections of the saints and so enable them to confirm their calling and election and be saved.
  -- p81, The Supremacy of God in Preaching by John Piper