Before Joseph died, he made his brothers promise him that when the time would come for the departure of Israel from Egypt, his coffin would be taken with them to the Land of Israel and buried there.

This promise was handed down to the children of Israel from generation to generation until the time came for the children of Israel to leave Egypt.

But where was Joseph's coffin? The Egyptians had placed it in the Nile and let it sink to the bottom.

Why did they do it? For two reasons. First of all, they had hoped that Joseph's coffin lying at the bottom of the Nile would bring them great fortune.

You see, in Egypt there is almost no rain during the year, and it would surely be a desert like Sahara, were it not for the river Nile, which waters and irrigates the land.

Even in those days, the Egyptians knew how to make use of this blessing. They dug canals and led the waters of the river to their fields and orchards. Their whole country depended upon the Nile, as it still does nowadays.

No wonder that the people of Egypt regarded the Nile as their god, and prayed to the river and worshipped it.

The other reason why they placed Joseph's coffin at the bottom of the Nile was because they knew that so long as the coffin would remain there, the children of Israel could nor leave Egypt, because they had promised.

When G‑d brought punishment upon the Egyptians, He first smote their god, the Nile, turning it into blood, and afterwards smote the Egyptians themselves.

When the day of the departure from Egypt came, Moses went to the bank of the river and called: "Joseph, Joseph. Your brethren are about to be freed from exile, and they want to keep their oath. Come up to the surface!"

Immediately, the coffin came up to the surface, and the children of Israel carried it with them to the Land of Israel.