וַיֹּ֣אמֶר יְהוָה֮ אֶל־מֹשֶׁה֒ אֱמֹ֣ר אֶֽל־אַהֲרֹ֗ן נְטֵ֤ה אֶת־יָדְךָ֙ בְּמַטֶּ֔ךָ עַל־הַ֨נְּהָרֹ֔ת עַל־הַיְאֹרִ֖ים וְעַל־הָאֲגַמִּ֑ים וְהַ֥עַל אֶת־הַֽצְפַרְדְּעִ֖ים עַל־אֶ֥רֶץ מִצְרָֽיִם׃
And the LORD said unto Moses: ‘Say unto Aaron: Stretch forth thy hand with thy rod over the rivers, over the canals, and over the pools, and cause frogs to come up upon the land of Egypt.’
Read kabbalistic (mystical) interpretation of Exodus 8:1: and classical mystical sources.