לא ידון רוחי באדם. כשיעלה נשמתן למעלה, איני אחזירה להם. ד"א איני בורא עוד נפש לאדם: לא ידון רוחי באדם לעולם, “My spirit will not rule within man forever;” this is a metaphor describing G–d as withholding man’s souls from participating in an afterlife after they had returned for Divine judgment. An alternate explanation: “I will no longer equip man with a heavenly soul.” (B’reyshit Rabbah 26,6.)
בשגם הוא בשר. נוטריקון הוא משה, חושבניה דדין כחושבניה דדין: בשגם הוא בשר, this word is an acrostic, the numerical value of its letters totalling 345, as does the numerical value of the letters in the word משה, (Moses) Moses lived for 120 years, meaning that he demonstrated that during 120 years on earth the human being can attain earthly perfection. This presupposes that such a human being had lived by the laws of the Torah. If man had not become corrupted, he could have attained such perfection by his own efforts without having to observe all the laws of the Torah, but it would have taken longer. This is why originally he was allowed to live to almost become one thousand years old. Once man only has a לב בשר, “a heart of flesh,” this process had to be drastically changed. [I have borrowed from the commentary of Rabbi Elie Munk in his “The call of the Torah.” Ed.]
והיו ימיו וכו'. ימי משה. ונ"ל דה"פ דקרא, לא ידון רוחי באדם, עד שיבא משה, שיהי' לו יצר טוב, דהיינו לב בשר, כדכתיב ונתתי לכם לב בשר, וזהו בשגם הוא בשר: