What does Genesis 21:17 mean?
The Lord had promised Abraham that Hagar and Ishmael would become a great nation. In other words, they would survive, and Ishmael's offspring would thrive. Based on the scene described in the prior verse, this seems especially unlikely. The pair have been wandering in the wilderness, out of water and with nowhere to go. Hagar has put Ishmael, about 16 years old, under the shade of bush and walked quite a distance away so as not to see him die.Now, though, God hears and arrives to save. Specifically, an angel of God calls from heaven to tell Hagar that God has heard the voice of the boy. Of course, God could have heard Hagar's voice, as well. It's not clear why the angel emphasizes that God has heard Ishmael's voice. Perhaps it was to comfort Hagar with the understanding that she was not alone in caring about Ishmael; God would care for the boy, as well.
Hagar first met the Lord, also in the wilderness, when she fled from Sarah's wrath after becoming pregnant by Abraham. That time, she called the Lord the "God of seeing." She said she had seen the One who looks after her (Genesis 16:13). Now the Lord makes clear to Hagar that He will look after Ishmael, as well.