Arise lift up the lad. In order that she might have more courage to bring up her son, God confirms to her what he had before often promised to Abraham. Indeed, nature itself prescribes to mothers what they owe to their children; but, as I have lately hinted, all the natural feelings of Hagar would have been destroyed, unless God had revived her, by inspiring new confidence, to address herself with fresh vigor to the fulfillment of her maternal office. With respect to the fountain or "well," [1] some think it suddenly sprung up. But since Moses says, that the eyes of Hagar were opened, and not that the earth was opened or dug up; I rather incline to the opinion, that, having been previously astonished with grief, she did not discern what was plainly before her eyes; but now, at length, after God has restored her vision, she begins to see it. And it is worthy of especial notice, that when God leaves us destitute of his superintendence, and takes away his grace from us, we are as much deprived of all the aids which are close at hand, as if they were removed to the greatest distance. Therefore we must ask, not only that he would bestow upon us such things as will be useful to us, but that he will also impart prudence to enable us to use them; otherwise, it will be our lot to faint, with closed eyes, in the midst of fountains.

Footnotes

1 - Ver. 19. "God opened her eyes, and she saw a well of water." "Quod ad fontem pertinet," are Calvin's words; but in his version it stands, "puteum aquae," a well of water. -- Ed

Arise, lift up the lad,.... She had set herself down at some distance, and now she is bid to rise up and go to the place where she had left her son, and raise aim up from the ground, on which he lay along:
and hold him in thine hand: or take hold on him with thine hand, and hold him up with it, he being so weak that he could not sit up without being supported:
for I will make him a great nation: which is a renewal of a promise before made both to her and to Abraham, Genesis 16:10; and by this Hagar is assured that he would recover and live, and become a man and the father of children, who in time would become a great nation; See Gill on Genesis 16:10, Genesis 17:20, Genesis 21:13, this shows that the Angel of God here speaking is God himself, or a divine Person, since none but he could make him a great nation.