John Wesley on Genesis 21:17

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.