Question: In Gen. 15:16, it says "In the fourth generation they [Abraham's descendants] shall come hither again." But, if we count Abraham, then their return occurred after seven generations: Abraham, Issac (Gen. 21:1-3), Jacob (Gen. 25:19-26), Levi (Gen. 35:22-23), Kohath (Ex. 6:16), Amramn (Ex. 6:18), and Moses (Ex. 6:20).
Response: In this case, the word "generation" in Genesis 15:16 is defined as being one "century" in length, in Genesis 15:13. This is because Abraham was a century old when his son Isaac was born. So, from Abraham's perspective, the words "generation" and "century" would be describing the same amount of time. And both of these verses in Genesis are viewing the future from Abraham's perspective. He is being told that his descendants would be in a foreign land for four centuries.
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