What does Genesis 16:16 mean?

Genesis 16 ends by reporting Abram's age at the time Ishmael was born. God had promised to make of Abram a great nation and to give to him the land of Canaan. The initial promises had been given when Abram was already seventy-five years old (Genesis 12:4). The arrival of an heir had not happened, yet, and from a human perspective seemed more and more unlikely. Even ten years after God's further promises (Genesis 16:3), Abram and Sarai were childless.

And so, Abram, at Sarai's urging, attempted to move things along through scheming and struggling on their own. The result was both conflict and blessing, with the promise of more conflict and blessing for generations to come. Hagar immediately conceived a son, but was at odds with Sarai (Genesis 16:4–6). And the child born to Sarai's servant Hagar was not the child of Abram's covenant with God. Ishmael would be blessed by God, but his descendants would be forever in conflict with others, especially their "kinsmen:" the other descendants of Abram (Genesis 16:11–12).

So, at 86 years old, Abram would obtain a son, but not the son of promise. In fact, Abram will wait another 13 years before God would reveal the details of His plan for the next stage of Abram's life.