The covenant completed.
I. THE ADMISSION OF SARAI.
1. The changed name. As on entering within the covenant the name of Abram was changed to Abraham, so, to signalize the reception of his spouse, Sarai was transformed into Sarah (vide Exposition), the transformation having in her case the same significance as it had in Abraham's. In particular it proclaimed that, like Abraham, Sarah was now a justified and regenerated believer in the Divine promise. N.B. There is only one gate of entrance to Christ's Church, viz; faith or conversion.
2. The guaranteed blessing. What is here affirmed of Sarai is that she should not only be received into the Church, but made a sharer of Abraham's blessing, i.e. become entitled to all the gracious provisions of the covenant. The blessing of Abraham belongs to all who are possessed of Abraham's faith. Christ's salvation is the common property of believers. And to all it is certain, as it was to Sarai. The "yea" concerning Sarai has now become for Christ's people "yea and amen."
3. The promised son. This was the first intimation that Sarai was to be the mother of the seed. The Eternal never hastens. God's disclosures of his own plans are ever slow, gradual, progressive, and mostly regulated by the faith of the recipients. When the fullness of the time arrives he is able to be minute, explicit, emphatic, as he was in intimating Isaac's birth:
4. The rejoicing husband. The laugh of gladness which escaped the patriarch, though partly owing to the reiterated promise of a son, was chiefly due to the announcement that Sarah was to be its mother. It was the joy of a husband in the happiness of a beloved wife, long tried, but at length about to be rewarded; it was also the joy of a believing husband in the well-founded assurance of his wife's interest in the covenant of grace.
II. THE EXCLUSION OF ISHMAEL.
1. The prayer of Abraham—
2. The answer of God—
III. THE ACQUIESCENCE OF ABRAHAM. This was signified by the patriarch's observance of the rite of circumcision, in regard to which his obedience was—
1. Immediate. There was no delay, no reluctance, no considering the question, but instantaneous compliance with the Divine directions. On the self-same day as God explained to him the provisions and conditions of the covenant, he declared his consent before God by the acceptance of the suggested sign. His behavior in this respect should be taken as a model by believers.
2. Cheerful. The rite of circumcision was of course attended with pain and something approaching to personal humiliation, and yet self-abasement and suffering were joyously assented to in view of the coming gift of the covenant. So should Christians delightedly accept tribulation and any sort of bodily indignity that God may impose, considering them as nothing in comparison with the eternal weight of glory.
3. Thorough-going. Prompt as to its time, willing in its spirit, the obedience of Abraham was also minute in its performance. The appointed ordinance was administered to himself, his son Ishmael, and every male domestic in his house, as God had said unto him. So God's people are required to observe all things written in the book of the covenant