Verse 13. - And the Lord said unto Abraham, Wherefore did Sarah laugh, - a question which must have convinced Abraham of the Speaker's omniscience. Not only had he heard the silent, inaudible, inward cachinnation of Sarah's spirit, but he knew the tenor of her thoughts, and the purport of her dubitations - saying, Shall I of a surely bear a child, whilst (literally, and I) am old? Sarah s mental cogitations clearly showed that the temporary obscuration of her faith proceeded from a strong realization of the weakness of nature, which made conception and pregnancy impossible to one like her, who was advanced in years; and accordingly her attention, as well as that of her husband, was directed to the Divine omnipotence as the all-sufficient guarantee for the accomplishment of the promise.

18:9-15 Where is Sarah thy wife? was asked. Note the answer, In the tent. Just at hand, in her proper place, occupied in her household concerns. There is nothing got by gadding. Those are most likely to receive comfort from God and his promises, who are in their proper place, and in the way of their duty, Lu 2:8. We are slow of heart to believe, and need line upon line to the same purport. The blessings others have from common providence, believers have from the Divine promise, which makes them very sweet, and very sure. The spiritual seed of Abraham owe their life, and joy, and hope, and all, to the promise. Sarah thinks this too good news to be true; she laughed, and therefore cannot as yet find in her heart to believe it. Sarah laughed. We might not have thought there was a difference between Sarah's laughter and Abraham's, ch. 17:17; but He who searches the heart, saw that the one sprung from unbelief, and the other from faith. She denied that she had laughed. One sin commonly brings in another, and it is not likely we shall strictly keep to truth, when we question the Divine truth. But whom the Lord loves he will rebuke, convict, silence, and bring to repentance, and if they sin before him.And the Lord said unto Abraham,.... This discovers who the person was that had been conversing with Abraham, that he was a divine Person, as appears by his name "Jehovah", as well as by his knowledge of Sarah's behaviour; he did not turn himself to her, that it might be more manifest that it was not upon the sight of her he judged she laughed, but from his own omniscience; and he chose rather to speak to her husband than to her, appearing as a stranger, and that he might reprove her:

wherefore did Sarah laugh, saying, shall I of a surety bear a child,

which am old? suggesting there was no reason for it, and signifying his displeasure and indignation at it.