One main stop that hinders Christians from rejoicing is, that they give themselves too much liberty to question their grounds of comfort and interest in the promises. This is wonderful, comfortable say they, but what is it to me, the promise belongs not to me? This ariseth from want of giving all ‘diligence to make their calling sure,’ 2 Pet. 1:10, to themselves. In watchfulness and diligence we sooner meet with comfort than in idle complaining. Our care, therefore, should be to get sound evidence of a good estate, and then likewise to keep our evidence clear; wherein we are not to hearken to our own fears and doubts, or the suggestion of our enemy, who studies to falsify our evidence, but to the word, and our own consciences enlightened by the Spirit; and then it is pride and pettishness to stand out against comfort to themselves. Christians should study to corroborate their title. We are never more in heaven, before we come thither, than when we can read our evidences. It makes us converse much with God, it sweetens all conditions, and makes us willing to do and suffer anything. It makes us have comfortable and honourable thoughts of ourselves, as too good for the service of any base lust, and brings confidence in God both in life and death.
But what if our condition be so dark that we cannot read our evidence at all?
Here look up to God’s infinite mercy in Christ, as we did at the first, when we found no goodness in ourselves, and that is the way to recover whatsoever we think we have lost. By honouring God’s mercy in Christ, we come to have the Spirit of Christ; therefore, when the waters of sanctification are troubled and muddy, let us run to the witness of blood. God seems to walk sometimes contrary to himself; he seems to discourage, when secretly he doth encourage, as the ‘woman of Canaan,’ Matt. 15:21–23; but faith can find out these ways of God, and untie these knots, by looking to the free promise and merciful nature of God. Let our sottish and rebellious flesh murmur as much as it will, Who art thou? and what is thy worth? yet a Christian ‘knows whom he believes,’ 2 Tim. 1:12. Faith hath learned to set God against all.
Richard Sibbes, The Complete Works of Richard Sibbes Vol. 1, p. 124