"Sarah laughed within herself."
1. The incongruity between a Divine promise and the sphere of its fulfillment is temptation to unbelief.
2. A disposition to measure the reality and certainty of the Divine by a human or earthly standard is sure to lead us to irreverence and sinful doubt.
3. There may be an inward and concealed working, known to God though not outwardly expressed. Which is still both an insult to him a d an injury to us.
4. The root of unbelief is in the ground of the soul. Sarah laughed because she was not prepared for the gracious promise. She was afraid of her own thoughts because they were not such as became her, and did dishonor to God's sufficiency and love. "She denied, saying, I laughed not." A more receptive and spiritual mind would have both risen above the incongruity and been incapable of the dissimulation.—R.