exodus 7:15 Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river's brink against he come; and the rod which was turned to a serpent shalt thou take in thine hand. - Free Bible Online

      15. Get thee unto Pharaoh--Now began those appalling miracles of judgment by which the God of Israel, through His ambassadors, proved His sole and unchallengeable supremacy over all the gods of Egypt, and which were the natural phenomena of Egypt, at an unusual season, and in a miraculous degree of intensity. The court of Egypt, whether held at Rameses, or Memphis, or Tanis in the field of Zoan (Ps 78:12), was the scene of those extraordinary transactions, and Moses must have resided during that terrible period in the immediate neighborhood.
      in the morning; lo, he goeth out unto the water--for the purpose of ablutions or devotions perhaps; for the Nile was an object of superstitious reverence, the patron deity of the country. It might be that Moses had been denied admission into the palace; but be that as it may, the river was to be the subject of the first plague, and therefore, he was ordered to repair to its banks with the miracle-working rod, now to be raised, not in demonstration, but in judgment, if the refractory spirit of the king should still refuse consent to Israel's departure for their sacred rites.

JFB.