Faith, I believe, has in it always a measure of assurance. For what is assurance? It is merely the larger growth and fuller development of faith. The nature of assurance is much misunderstood. It is often considered something distinct from faith. This is not the case. It is merely faith in a fuller, larger development. The word "assurance" in the original has a very simple, yet beautiful meaning. It means literally "a full bearing;" and the word is applied sometimes to a large crop of corn or fruit, and sometimes to the tide coming in with a fuller wave. Now it is the same corn which grows in the fields, whether the crop be much or little; it is the same tide that comes up the river whether in a scanty or full flow. So it is with assurance and faith: it is the same faith, only increased, enlarged, bearing more abundant fruit, or flowing in a more abundant tide.
Assurance in Scripture is not confined to faith; there is "the full assurance of understanding" (Col. 2:2), that is, a fuller measure and amount, a greater enlargement of understanding to know the truth of God. The understanding is the same; but there is a larger measure of it. So there is the full assurance of hope, that is, a hope strengthened and enlarged, bearing more fruit and flowing in a fuller tide. But it is the same hope; the same in kind, though larger in degree; a stronger anchor, and yet an anchor still (Heb. 6:19). Similarly there is the full assurance of faith (Heb. 10:22), that is, a larger, fuller measure of faith; a richer crop, a more abundant tide.
Thus you have a measure of the assurance of faith if you have faith at all. In fact, if you have no assurance of the truth of these things, why do you follow after them? Why do you hang upon them, why do you hope in them, and why do you seek the power and experience of them in your soul? Have you not arrived at this point yet? "We have not followed cunningly devised fables; these things that I am following after are realities; these objects set before me are certainties." I grant that you may be much exercised about your interest in them. Still, unless you know that they are certainties, why do you believe them? Why are you anxious to know your interest in them? Why do you sink in doubt and fear for want of clearer evidences of an interest in them? And why do you spring up in peace and joy the moment that a little light from them beams upon your soul, and a little sweetness out of them drops into your heart? Because you know that these things are realities. So far then you have an assurance that they are certainties, and in due time, as God is pleased, you will have the assurance in your own breast, not only that they are certainties, but that you have them in your own sure and certain possession.