"God said to Moses, 'Go to Pharaoh' "
Pharaoh did not know the name of God denoted as Y-H-V-H (יהוה) and denied its power, since he said “I do not recognize God (יהוה).” He did, however, recognize the name of God Elohim (אלהים), since his magicians told him, “This is the finger of God (Elohim).”
This is because Pharaoh was drawing his sustenance from the Cosmic Man, but only from his youthful, unrefined mind, which consists of three parts, called meat steward, wine steward, and bread steward. All of them represent the name of God Elohim, the name that denotes the natural course of events, cause and effect, and crime and punishment. Even when through the plagues Pharaoh was ready to accept the name of God Y-H-V-H – which denotes God's presence in everyday affairs – he was only ready to accept the judgment and punishment parts of this involvement, since he said “God (Y-H-V-H) is correct, and I am a sinner” - and the first letters of this phrase spell out Y-H-V-H (יהוה).
Thus even in his defeat Pharaoh was insisting on his understanding of God as a Vengeful Judge. To counteract this, God said “I will bring my signs (אותותי), which should be read as "signs of the letter yud" (אותות - י), and the gematria of yud is 10, corresponding to the spelling of the name Y-H-V-H (יוד הי ויו הי), which has 10 letters. This is also hinted to by the frogs that went into “your midst” - literally into the midst of Pharaoh.
Art: Alois Stoff - In Search Of The Pharaohs