Some Bibles render Gen. 2:21-24 this way:
21 And Jehovah God caused a deep sleep to fall upon the man, and he slept; and he took one of his ribs, and closed up the flesh instead thereof: 22 and the rib, which Jehovah God had taken from the man, made he a woman, and brought her unto the man. 23 And the man said, This is now bone of my bones, and flesh of my flesh: she shall be called Woman, because she was taken out of Man. 24 Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh. - ASV
Because no quotation marks were used, some have expressed confusion as to whether Adam finished talking at the end of verse 23 or verse 24. If Adam spoke these words to the end of verse 24, how could Adam know about leaving fathers and mothers when he had never witnessed children growing up with their parents?
The confusion can be eliminated by examining other translations for Gen. 2:23. Many Bible translations render Adam's quote as stopping before the sentence beginning with "Therefore". (Notice the NIV, CBJ, ESV, GW, GNT, HNV, NAS, NCV, NIRV, NKJV, NLT, NRS, RSV, etc.)
So the sentence: "Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh.” was not understood to have been uttered by Adam but was rather a continuation of the account by Moses, the writer of Genesis.