Then the angel added, “I will greatly multiply your offspring so that they will be too numerous to count.”
10. I will multiply thy seed exceedingly For the purpose of mitigating the offense, and of alleviating what was severe in the precept, by some consolation, he promises a blessing in the child which she should bear. God might indeed, by his own authority, have strictly enjoined what was right; but in order that Hagar might the more cheerfully do what she knew to be...
We may suppose that the angel having given Hagar that good counsel (Gen 16:9) to return to her mistress she immediately promised to do so, and was setting her face homeward; and then the angel went on to encourage her with an assurance of the mercy God had in store for her and her seed: for God will meet those with mercy that are returning to their duty.
Commenting on Genesis 16:10-14
And the angel of the Lord said unto her,.... The same as before, who, by what follows, appears to be Jehovah himself: I will multiply thy seed exceedingly; not that she should have many children herself, for that she had more than this one she now went with, is not certain; but that that seed she had conceived should be exceedingly multiplied, and he should...