Exodus 7:15

הנה יצא המימה LO, HE GOETH OUT UNTO THE WATER to ease himself. For he claimed to be a god and asserted that because of his divine power he did not need to ease himself; and therefore he used to rise early and go to the Nile and there eased himself in secret (Midrash Tanchuma, Vaera 14; Exodus Rabbah 9:8).

לֵ֣ךְ אֶל־פַּרְעֹ֞ה בַּבֹּ֗קֶר הִנֵּה֙ יֹצֵ֣א הַמַּ֔יְמָה וְנִצַּבְתָּ֥ לִקְרָאת֖וֹ עַל־שְׂפַ֣ת הַיְאֹ֑ר וְהַמַּטֶּ֛ה אֲשֶׁר־נֶהְפַּ֥ךְ לְנָחָ֖שׁ תִּקַּ֥ח בְּיָדֶֽךָ׃

Get thee to Par῾o in the morning; lo, he goes out to the water; and thou shalt stand by the River’s brink to meet him; and the rod which was turned to a snake shalt thou take in thy hand.