Genesis 17

10. Every man child among you shall be circumcised--This was the sign in the Old Testament Church as baptism is in the New, and hence the covenant is called "covenant of circumcision" ( Acts 7:8 , Romans 4:11 ). The terms of the covenant were these: on the one hand Abraham and his seed were to observe the right of circumcision; and on the other, God promised, in the event of such observance, to give them Canaan for a perpetual possession, to be a God to him and his posterity, and that in him and his seed all nations should be blessed.

15, 16. As for Sarai . . . I will . . . give thee a son also of her--God's purposes are gradually made known. A son had been long ago promised to Abraham. Now, at length, for the first time he is informed that it was to be a child of Sarai.

17. Abraham fell upon his face, and laughed--It was not the sneer of unbelief, but a smile of delight at the improbability of the event ( Romans 4:20 ).

18. O that Ishmael might live before thee--natural solicitude of a parent. But God's thoughts are not as man's thoughts [ Isaiah 55:8 ].

19, 20. The blessings of the covenant are reserved for Isaac, but common blessings were abundantly promised to Ishmael; and though the visible Church did not descend from his family, yet personally he might, and it is to be hoped did, enjoy its benefits.