Note 3 at Acts 7:6: This is exactly the precise period of time that God prophesied to Abram in Genesis 15:13. However, because Exodus 12:40-41 clearly states that the children of Israel came out of Egypt after 430 years, some people have argued that Genesis 15:13 and this reference here were only a round number, not intended to be accurate.

This difference of 30 years becomes very important, however, when you subtract the 40 years (v. 30) that Moses spent in the wilderness after his failed deliverance attempt, from the 430 years of actual bondage. This means that Moses killed the Egyptian in an attempt to deliver the Jewish people in the 390th year of their sojourn, or 10 years before the time period prescribed by God in Genesis 15:13 was up. It is most probable that the 400 years spoken of by God in Genesis 15:13 and also here was the exact time that the Lord had intended before He delivered the Jewish people from Egypt, but Moses' self-will that was exhibited in killing the Egyptian (Ex. 2:12) cost Moses 40 years in the desert and the children of Israel 30 years of extra bondage.

The Jews were not slaves in Egypt the entire 400 years. Abram came into Canaan when he was 75 years old (Gen. 12:4). The covenant of Genesis 15:13-16 that prophesied the 400 years, took place at least a year before Ishmael's birth (Gen. 16:15). That means that Abram could not have been over 85 when this covenant was made (Gen. 16:16 minus 9 months) and he could have been in his seventies. Abraham then had Isaac at 100 years of age. When Isaac was 60 years old, Jacob and Esau were born (Gen. 25:26), and Jacob moved to Egypt with his children when he was 130 years old (Gen. 47:9). That was not more than 215 years but at least 205 years after the covenant of Genesis 15 when God spoke of the 400 years that Abram's seed would be afflicted.

Joseph was 39 when his father Jacob (or Israel) came into Egypt (Gen. 41:46-47 with 45:6), and the Israelites enjoyed freedom throughout the rest of Joseph's life which lasted another 71 years (Gen. 50:22). That would bring the total lapsed time from the prophecy of Genesis 15 to the death of Joseph to 276-286 years.

Exodus 1:8 does not clearly state how long it was after the death of Joseph until another king arose who knew not Joseph, but it can be assumed that it was at least a period of some years. That would mean that the total time that the Israelites could have been slaves to the Egyptians was, at the most, 150 years, and probably much less than that.

The first century historian, Josephus, arrived at this same conclusion when he wrote, "The Hebrews left Egypt 430 years after our forefather Abraham came into Canaan, but 215 years only after Jacob removed into Egypt" (Antiq. ii. 15,2).