Genesis 15:13 "Then the LORD said to Abram, "Know for certain that your offspring will be sojourners in a land that is not theirs and will be servants there, and they will be afflicted for four hundred years."--God knew His people would be strongest if their nation began in trial and not in blessing.
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17:18 "And Abraham said to God, "Oh that Ishmael might live before you!" --Most of us would rather settle for the blessing of Ishmael, the blessing we can see, rather than face the uncertainty of the blessing of Isaac. But is the Isaac blessing that God has called us to. The blessing that we cannot produce. The blessing that can only come from Him. This is the blessing that changes everything.