Exodus 7:25

"And seven days were fulfilled, after that the LORD had smitten the river."

Cross References (ranked by relevance)

So Gad came to David, and told him, and said unto him, Shall seven years of famine come unto thee in thy land? or wilt thou flee three months before thine enemies, while they pursue thee? or that there be three days’ pestilence in thy land? now advise, and see what answer I shall return to him that sent me.

Exodus 10:23

They saw not one another, neither rose any from his place for three days: but all the children of Israel had light in their dwellings.