God told Abraham:
Genesis 15:13... Know of a surety that thy seed shall be a stranger in a land that is not theirs, and shall serve them; and they shall afflict them four hundred years; 14 And also that nation, whom they shall serve, will I judge: and afterward shall they come out with great substance. 15 And thou shalt go to thy fathers in peace; thou shalt be buried in a good old age. 16 But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full.
At first reading we might think that 400 years refers to the time in Egypt but it can also refer to the time of sojourning which included (but was not limited to) the time spent in Egypt. While Joseph was alive, the Egyptians did not afflict the Hebrews. Joseph died 110 years old, some 80 years after Israel went into Egypt and it was some time after that that the affliction began and they were brought into bondage.
Acts 7:6 And God spake on this wise, That his seed should sojourn in a strange land; and that they should bring them into bondage, and entreat them evil four hundred years.
The time that Abraham’s seed was to be a stranger in a land that was not theirs was to be 400 years, but they would return out of Egypt to Canaan in the fourth generation.
A generation is not one hundred years, so for this to be true we must assume that Abraham’s seed being ‘a stranger in a land that was not theirs’ began not in Egypt, but after Isaac (his promised seed) was born in the land of Canaan.
We can determine that the fourth generation refers to the number of generations which would be in Egypt.
If we look at the genealogy from Jacob to Moses we have: Levi – Kohath – Amram – Moses. Moses was the fourth generation of those who went down into Egypt.
Exodus 6:16... these are the names of the sons of Levi according to their generations... Kohath... 18 And the sons of Kohath; Amram... 20 And Amram took him Jochebed his father’s sister to wife; and she bare him Aaron and Moses... 26 These are that Aaron and Moses, to whom the LORD said, Bring out the children of Israel from the land of Egypt according to their armies.
Exodus 12:40-41 Now the sojourning of the children of Israel, who dwelt in Egypt, was four hundred and thirty years. 41 And it came to pass at the end of the four hundred and thirty years, even the selfsame day it came to pass, that all the hosts of the LORD went out from the land of Egypt.
The selfsame day refers to the exodus occurring exactly 430 years after the day that God made the covenant with Abraham.
In the New Testament the matter is made certain for us by the inspired comment of Paul to the Galatians:
Galatians 3:17 And this I say, that the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect.
This clearly states that the Law of Moses was given 430 years after God made the Covenant with Abraham.
Abraham entered Canaan when he was 75 years old (Genesis 12:4) Isaac was born when he was 100 years old. Jacob was born when Isaac was 60 years old (Gen 25:26) and he went down into Egypt aged 130 (Gen 47:9). From Abraham entering Canaan to Jacob going into Egypt was 25 + 60 + 130 = 215 years.
The difficulty is determining when God made the Covenant with Abraham.
If we assume that God made the Covenant when Abraham entered Canaan at 75 years old, then the time that Israel spent in Egypt would be 430 – 215 = 215 years.
If we assume that the Covenant was made at the same time as the prophecy in Genesis 15, perhaps some 5 years after Abraham entered the land then the time spent in Egypt would be 215 – 5 = 210 years.
We might reasonably conclude from this that the time Israel actually spent in Egypt was somewhere between 210 and 215 years.
I hope you have found this helpful.
God bless you,