Faith is not then properly the condition of the Covenant, upon the performance of which, they have a right and title to it; but a choice effect of it, and a singular means for the application of the promises, and fetching in of Covenant blessings to the Soul: by that the Promise, or what is in the Promise, is given to it, and Faith having thus to do with the Promises, it must needs have an aptitude above other Graces, above Sanctification and Evangelical obedience to witness a Soul’s interest in the everlasting Covenant.
By Faith the Soul maketh out [i.e. looks] to Jesus Christ in the Free Promise, as he alone that giveth it subsistence in spiritual Life…Christians live by Faith, by what is laid up in Divine Promises, by these things they live.
I have often thought, if Christians did give more attendance to such direct acts of Faith, and spent less time in questioning their conditions, or giving way to doubtings about them, they would find their interest in the Covenant cleared up, yea and consolation also coming in as by the by.
We are to take heed, that we do not ground and bottom our consolation on the qualifications within, but on the promise itself (or the Lord therein) without. Many are drawing and fetching their comfort from their faith and other graces, and lay the stress of it there, and accordingly are up and down, ebbing and flowing therein, instead of fetching it from the Lord in the promise, an immutable thing, Heb. 6.18. by the means of faith and taking that and other graces only as evidences of interest in it. Some, because they are weary and heavy laden, thence take their rest
and refreshment, wheras they are called out of themselves, to come for it to Jesus Christ, Matth. 11.28. When qualifications lie most dark, or are most clearly discerned, yet we should not look so much to these, as to Jesus Christ in the promise for Consolation … when Jesus Christ was upon Earth, he performed the office of a Mediator as to satisfaction; and now he is in heaven, he doth it still as to intercession, Heb. 7.25. He presenteth his obedience continually to the Father for our obtainment for what he hath purchased. Would we have any foederal blessings, the Law written in our heart in more lively characters, the Lord witnessed more fully to be our God, sin to be pardoned? Let our faith be acting upon him as one that mediateth for our obtainment of all; for he is the Mediator, not of the Old, but of the New and Better Testament, which is established upon better Promises.
Petto on the Source of Assurance