For Sarah conceived, and bare Abraham a son in his old age, at the set time of which God had spoken to him.
Sarah conceived — Sarah by faith, received strength to conceive, Hebrews 11:11. God therefore, by promise, gave that strength. Abraham was old, and Sarah old, and both as good as dead, and then the word of God took place.
 And Abraham circumcised his son Isaac being eight days old, as God had commanded him.
He circumcised his son — The covenant being established with him, the seal of the covenant was administered to him.
 And Sarah said, God hath made me to laugh, so that all that hear will laugh with me.
And Sarah said, God has made me to laugh — He hath given me both cause to rejoice, and a heart to rejoice. And it adds to the comfort of any mercy to have our friends rejoice with us in it, See Luke 1:58.
They that hear will laugh with me — Others will rejoice in this instance of God's power and goodness, and be encouraged to trust in him.
 And Sarah saw the son of Hagar the Egyptian, which she had born unto Abraham, mocking.
Sarah saw the son of the Egyptian mocking — Mocking Isaac no doubt, for it is sad, with reference to this, Galatians 4:29, that he that was born after the flesh, persecuted him that was born after the spirit. Ishmael is here called the son of the Egyptian, because (as some think) the four hundred years affliction of the seed of Abraham by the Egyptians began now, and was to be dated from hence.
 Wherefore she said unto Abraham, Cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac.
Cast out the bond-woman — This was a type of the rejection of the unbelieving Jews, who, though they were the seed of Abraham, yet, because they submitted not to the gospel-covenant, were unchurched and disfranchised. And that, which above any thing provoked God to cast them off, was, their mocking and persecuting the gospel-church, God's Isaac, in his infancy.
 And the thing was very grievous in Abraham's sight because of his son.
The thing was very grievous in Abraham's sight — it grieved him that Ishmael had given such provocation. And still more that Sarah insisted upon such a punishment.
 And also of the son of the bondwoman will I make a nation, because he is thy seed.
The casting out of Ishmael was not his ruin. He shall be a nation because he is thy seed - We are not sure that it was his eternal ruin. It is presumption to say, that all these who are left out of the external dispensation of God's covenant are excluded from all his mercies. Those may be saved who are not thus honoured.
 And Abraham rose up early in the morning, and took bread, and a bottle of water, and gave it unto Hagar, putting it on her shoulder, and the child, and sent her away: and she departed, and wandered in the wilderness of Beersheba.
And Abraham rose up early in the morning — We may suppose immediately after he had in the night-visions received orders to do this.
 And God heard the voice of the lad; and the angel of God called to Hagar out of heaven, and said unto her, What aileth thee, Hagar? fear not; for God hath heard the voice of the lad where he is.
God heard the voice of the lad — We read not of a word be said; but his sighs and groans, cried loud in the ears of the God of mercy. An angel was sent to comfort Hagar, who assures her, God has heard the voice of the lad where he is - Though he be in the wilderness; for wherever we are, there is a way open heavenwards; therefore lift up the lad, and hold him in thy hand - God's readiness to help us when we are in trouble must not slacken, but quicken our endeavours to help ourselves. He repeats the promise concerning her son, that he should be a great nation, as a reason why she should bestir herself to help him.
 Wherefore he called that place Beersheba; because there they sware both of them.
Beer-sheba — That is, the well of the oath, in remembrance of the covenant that they sware to, that they might be ever mindful of it.
 And Abraham planted a grove in Beersheba, and called there on the name of the LORD, the everlasting God.
And Abraham planted a grove — For a shade to his tent, or perhaps an orchard of fruit trees; and there, though we cannot say he settled, for God would have him while he lived to be a stranger and a pilgrim, yet he sojourned many days.
And called there on the name of the Lord — Probably in the grove he planted, which was his oratory, or house of prayer: he kept up publick worship, to which probably his neighbours resorted, and joined with him. Men should not only retain their goodness wherever they go, but do all they can to propagate it, and make others good.
The everlasting God — Though God had made himself known to Abraham as his God in particular; yet he forgets not to give glory to him as the Lord of all, the everlasting God, who was before all worlds, and will be when time and days shall be no more.