פּירוש אויף שמות 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).

הנה יוצא המימה, according to Rashi, Pharaoh went to the Nile every morning in order to have his bowel movement, as having declared himself a deity, he could not allow his subjects to think that he like they had to excrete his undigested food daily. Seeing that the area where he performed this rite was a dirty area, G-d had not told Moses “בא אל פרעה” as if he were to dress up for an interview at Pharaoh’s Palace. The meaning of בא when G-d speaks to Moses, always implies that He is accompanying him as He had promised in Exodus 3,12.

הנה יוצא המימה, as do most ministers, in order to take their morning stroll. Sometimes they go for a short gallop on their horse.