Ibn Ezra on Leviticus 11:36

באר. בלשון הקדש לשון נקבה והיא הנובעת וכן כהקיר ברר מימיה ובור כרוי או חפור למטה השמים אם כן תהיה הבאר כמו מעיין ואין צורך להזכיר הנחל ויהיה מקוה מים סמוך אל בור כי יש בור אין בו מים ויש אומרים כי הוא חסר וי״ו כמו ראובן שמעון שמש ירח: A CISTERN. The Hebrew word be’er (well) is a feminine. It bubbles forth. Compare, As a well (bir)⁹¹This is the ketiv. Bir is a variant of be’er. Translated according to I.E. welleth with her waters (Jer. 6:7). However, a bor (cistern) is dug or excavated to store the rain from the sky. If so,⁹²If the water in the well bubbles forth. the well is a fountain.⁹³Mentioned in our verse. There is no need to mention rivers.⁹⁴In our verse, for the waters in the rivers have their origin in underground fountains. Mikveh mayim (a gathering of water) is connected to bor (cistern),⁹⁵Bor mikveh mayim means a cistern wherein is a gathering of water (v. 36). for there are borot (cisterns) without water.⁹⁶Hence mikveh mayim follows bor. Some say that mikveh is missing a vav.⁹⁷Mikveh mayim should be read as if written, u-mikveh mayim. According to this interpretation our verse reads, or a cistern, or a gathering of water. Compare, Reuben, Simeon (Ex, 1:2),⁹⁸Which is to be interpreted as if written, re’uven ve-shimon (Reuben and Simon). and shemesh yare’ach (the sun moon) (Hab. 3:11).⁹⁹Which is to be interpreted as if written, shemesh ve-yare’ach (the sun and the moon).

ונגע בנבלתם. המים הנוגעים בנבלתם יהיו טמאים: BUT HE WHO TOUCHETH THEIR CARCASS. The water that touches their carcasses will be unclean.¹⁰⁰Water that is removed from the ground.