Bereshit 

בראשית

The Sages discuss the creation of the first woman from a perspective that views man and woman as two halves of a single entity. 

Rabbi Yirmeya ben Elazar said: When the Holy One, blessed be He, created Adam the first person, He created him androgynous.<footnote data-num="12"/> That is what is written: “Male and female He created them” (Genesis 5:2). Rabbi Shmuel bar Nahman said: When the Holy One, blessed be He, created Adam the first person, He created him with two fronts,<footnote data-num="13"/> and He then split him and made for him two backs – one here and one there.<footnote data-num="14"/> Rabbi Yohanan said: Adam and Eve were created at the developmental age of approximately twenty years old. <source>(<i>Bereshit</i> <i>Rabba</i> 8, 14) </source>