I recently wrote elsewhere on the covenant stipulation of the New and Old Covenant. The historical testimony of the Canons of Dort aligns with the idea of "gospel threats,"
"And, just as it has pleased God to begin this work of grace in us by the proclamation of the gospel, so God preserves, continues, and completes this work by the hearing and reading of the gospel, by meditation on it, by its exhortations, threats, and promises, and also by the use of the sacraments." - The Fifth Main Point, Article 14: God's Use of Means in Perseverance