Here's a helpful statement on assurance from William Gurnall:
Faith, in time, after much communion with God, acquaintance with the Word, and experience of His dealings with the soul, may flourish into assurance. But as the root truly lives before the flower appears, and continues when that hath shed its beautiful leaves, and gone again, so doth true justifying faith live before assurance comes and after it disappears.... Assurance is, as it were, the cream of faith.
Now you know there is milk before there is cream; this riseth not but after some time standing, and there remains milk after it is skimmed off. How many, alas, of the precious saints of God must we shut out from being believers if there is no faith but what amounts to assurance?
...Assurance is like the sunflower, which opens with the day and shuts with the night. It follows the motion of God's face. If that looks smilingly on the soul, it lives; if that frowns or hides itself, it dies. But faith is a plant that can grow in the shade, a grace that can find the way to heaven in a dark night. It can 'walk in darkness', and yet 'trust in the name of the Lord' (Isaiah 50:10).
-from William Gurnall's Christian in Complete Armour
