Genesis 15:15

And thou shalt go to thy fathers in peace; thou shalt be buried in a good old age.

The promise was given in the covenant vision in which Abraham was told that he himself would not immediately possess the promised land. To Abraham personally it assured a peaceful death and burial in advanced old age. In that same setting his descendants were foretold to go down to Egypt because famine threatened their lives. There they would suffer before settling in Canaan, enduring oppression in Egypt for nearly four hundred years.

God permitted that oppression so that they would turn to Him, yet He did not forsake them because of His covenant with Abraham. He would then deliver them by a powerful act, revealing Himself as ruler over all nations and their gods. Judgment on the Amorites was likewise delayed until their iniquity was full, with God giving them more than four hundred years to repent. When instead they hardened themselves in wrongdoing and made war on Israel, their probation ended and judgment came.