And Abram called Hagar had been commanded to give that name to her son; but Moses follows the order of nature; because fathers, by the imposition of the name, declare the power which they have over their sons. We may easily gather, that Hagar, when she returned home, related the events which had occurred. Therefore, Abram shows himself to be obedient and grateful to God: because he both names his son according to the command of the angel, and celebrates the goodness of God in having hearkened to the miseries of Hagar.

And Hagar bare Abram a son, etc. - It appears, therefore, that Hagar returned at the command of the angel, believing the promise that God had made to her.
Called his son's name - Ishmael - Finding by the account of Hagar, that God had designed that he should be so called. "Ishmael," says Ainsworth, "is the first man in the world whose name was given him of God before he was born."
In the preceding chapter we have a very detailed account of the covenant which God made with Abram, which stated that his seed would possess Canaan; and this promise, on the Divine authority, he steadfastly believed, and in simplicity of heart waited for its accomplishment. Sarai was not like minded. As she had no child herself, and was now getting old, she thought it necessary to secure the inheritance by such means as were in her power; she therefore, as we have seen, gave her slave to Abram, that she might have children by her. We do not find Abram remonstrating on the subject; and why is he blamed? God had not as yet told him how he was to have an heir; the promise simply stated, He that shall come forth out of thine own bowels shall be thine heir, Genesis 15:4. Concubinage, under that dispensation, was perfectly lawful; therefore he could, with equal justice and innocence, when it was lawful in itself, and now urged by the express desire of Sarai, take Hagar to wife. And it is very likely that he might think that his posterity, whether by wife or concubine, as both were lawful, might be that intended by the promise.
It is very difficult to believe that a promise which refers to some natural event can possibly be fulfilled but through some natural means. And yet, what is nature but an instrument in God's hands? What we call natural effects are all performed by supernatural agency; for nature, that is, the whole system of inanimate things, is as inert as any of the particles of matter of the aggregate of which it is composed, and can be a cause to no effect but as it is excited by a sovereign power. This is a doctrine of sound philosophy, and should be carefully considered by all, that men may see that without an overruling and universally energetic providence, no effect whatever can be brought about. But besides these general influences of God in nature, which are all exhibited by what men call general laws, he chooses often to act supernaturally, i.e., independently of or against these general laws, that we may see that there is a God who does not confine himself to one way of working, but with means, without means, and even against natural means, accomplishes the gracious purposes of his mercy in the behalf of man. Where God has promised let him be implicitly credited, because he cannot lie; and let not hasty nature intermeddle with his work.
The omniscience of God is a subject on which we should often reflect, and we can never do it unfruitfully while we connect it, as we ever should, with infinite goodness and mercy. Every thing, person, and circumstance, is under its notice; and doth not the eye of God affect his heart? The poor slave, the stranger, the Egyptian, suffering under the severity of her hasty, unbelieving mistress, is seen by the all-wise and merciful God. He permits her to go to the desert, provides the spring to quench her thirst, and sends the Angel of the covenant to instruct and comfort her. How gracious is God! He permits us to get into distressing circumstances that he may give us effectual relief; and in such a way, too, that the excellence of the power may appear to be of him, and that we may learn to trust in him in all our distresses. God delights to do his creatures good.
In all transactions between God and man, mentioned in the sacred writings, we see one uniform agency; the great Mediator in all, and through all; God ever coming to man by him, and man having access to God through him. This was, is, and ever will be the economy of grace. "The Father hath sent me: - and no man cometh unto the Father but by me." God forbid that he should have cause to complain of us, "Ye will not come unto me, that ye might have life."

And Hagar bare Abram a son,.... Being returned to his house, and received by him, and reconciled to Sarai, she brought forth a son to Abram, according to the prediction of the angel:
and Abram called his son's name, which Hagar bare, Ishmael; and this name Jarchi suggests he gave by the inspiration of the Holy Spirit that dwelt in him: but it is highly reasonable to suppose, that Hagar upon her return reported to Abram the whole of the conversation she had with the angel; wherefore Abram believing what she said, in obedience to the order and command of the angel, gave him this name.

Having returned to Abram's house, Hagar bare him a son in his 86th year. He gave it the name Ishmael, and regarded it probably as the promised seed, until, thirteen years afterwards, the counsel of God was more clearly unfolded to him.