And the Lord spake unto Moses and unto Aaron After he had given them their commission, and instructions to go to Pharaoh, and a little before they went in to him:
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"When Pharaoh speaks to you, saying, 'Work a miracle,' then you shall say to Aaron, 'Take your staff and throw it down before Pharaoh, that it may become a serpent.' "
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So Moses and Aaron came to Pharaoh, and thus they did just as the LORD had commanded; and Aaron threw his staff down before Pharaoh and his servants, and it became a serpent.