This past year I've been returning to the Heidelberg Catechism, Belgic Confession, and Canons of Dort (the so-called 'Three Forms of Unity'). Simply magnificent documents. Not a word is wasted; Bible-saturated; reverent toward God; careful; unafraid to say the hard truth, however humanly counterintuitive it might be, if Scripture leads them there; and wonderfully encouraging, strengthening. Anyhow here's how the Canons of Dort (which gave us our five points of Calvinism) express the gospel's role in 'perseverance of the saints.'
God's Use of Means in Perseverance
And, just as it has pleased God to begin this work of grace in us by the proclamation of the gospel, so he preserves, continues, and completes his 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. (V.14)