What does Genesis 15:13 mean?
The Lord will soon complete a covenant ritual between Himself and Abram, a ritual that will specify, in part, the boundaries of future Israel to be occupied and possessed by Abram's descendants.First, however, God will reveal to Abram a prophecy about the difficult future his descendants will face before they occupy the Promised Land. Abram's offspring, God says, will be strangers, sojourners, serving others in a land that is not their own. They will be afflicted or mistreated for 400 years. God is referring to Israel's slavery in Egypt, after the death of Joseph (Genesis 50:26) and before the story of Moses and the Exodus (Exodus 1:1–8). As is common in all forms of literature, the reference to time here is a generic, round number. It is perhaps meant to refer to four generations that will come and go during that time. Exodus 12:40 and Galatians 3:17 specify the length of that captivity as 430 years.
God is making clear to Abram that, though the promise of the land will be kept, it will be kept in God's own time, centuries in the future.
Genesis 15:1–21 falls between Abram's heroic rescue of Lot in Genesis 14 and his less-than-heroic choice to have a child with his wife's servant in chapter 16. Chapter 15 features Abram's hard questions to the Lord about how the lofty promises of uncountable descendants and possession of the land will be kept. God responds, in part, by formalizing His covenant promises to Abram with an elaborate ritual. He also reveals to Abram details about the difficult circumstances his descendants will face before they come back to take possession of the land ''in the fourth generation.''
Genesis 15 consists entirely of a long encounter between the Lord and Abram. When the ''word of the Lord'' comes to Abram in a vision to bring reassurance of God's support for him, Abram takes the opportunity to press God with questions. Abram asks both about his childlessness and how he can know he will one day possess the land of Canaan. God responds, and Abram believes. God's response includes leading Abram through a covenant ritual involving slaughtered animals, as well as a prophecy about the future of Abram's descendants before the time will come to occupy the Promised Land.
