Genesis 15:13

Four hundred years - "Which began," says Mr. Ainsworth, "when Ishmael, son of Hagar, mocked and persecuted Isaac, Genesis 21:9; Galatians 4:29; which fell out thirty years after the promise, Genesis 12:3; which promise was four hundred and thirty years before the law, Galatians 3:17; and four hundred and thirty years after that promise came Israel out of Egypt, Exodus 12:41."

Know, know thou. - Know certainly. This responds to Abram's question, Whereby shall I know? Genesis 15:8. Four hundred years are to elapse before the seed of Abram shall actually proceed to take possession of the land. This interval can only commence when the seed is born; that is, at the birth of Isaac, when Abram was a hundred years of age and therefore thirty years after the call. During this interval they are to be, "first, strangers in a land not theirs" for one hundred and ninety years; and then for the remaining two hundred and ten years in Egypt: at first, servants, with considerable privilege and position; and at last, afflicted serfs, under a hard and cruel bondage. At the end of this period Pharaoh and his nation were visited with a succession of tremendous judgments, and Israel went out free from bondage "with great wealth" Exodus 12-14. "Go to thy fathers." This implies that the fathers, though dead, still exist. To go from one place to another implies, not annihilation, but the continuance of existence. The doctrine of the soul's perpetual existence is here intimated. Abram died in peace and happiness, one hundred and fifteen years before the descent into Egypt.

15:13 Thy seed shall be strangers — So they were in Canaan first, Psalms 105:11,12, and afterwards in Egypt: before they were lords of their own land, they were strangers in a strange land. The inconveniences of an unsettled state make a happy settlement the more welcome. Thus the heirs of heaven are first strangers on earth.

And them they shall serve — So they did the Egyptians, Exodus 1:13. See how that which was the doom of the Canaanites, Genesis 9:25, proves the distress of Abram's seed: they are made to serve; but with this difference, the Canaanites serve under a curse, the Hebrews under a blessing.

And they shall afflict them — See Exodus 1:11. Those that are blessed and beloved of God are often afflicted by wicked men. This persecution began with mocking, when Ishmael the son of an Egyptian, persecuted Isaac, Genesis 21:9, and it came at last to murder, the basest of murders, that of their new born children; so that more or less it continued 400 years.