Our assurance of justification, adoption, grace, and salvation, is syllogistic: whoever believes on the Son of God, shall not perish, but have life everlasting. But I believe on the Son of God; therefore, I shall not perish. Whoever judge themselves, shall not be judged of the Lord. But I judge myself; therefore etc. Whoever loveth the brethren, hath passed from death to life. But I love the brethren; therefore, etc. In these or the like proofs, it is the Spirit of grace which gives us the right understanding, and firm belief of the proposition.
– George Gillespie
The Spirit of Grace gives Assurance
