GEN869 Purity was the special quality of Avraham Avinu, a”h – he rectified all the internal forces that are part and parcel of the body. As the midrash states (Bereshis Rabbah 46:3): “HaKadosh Baruch Hu said to Avraham, ‘There is no impurity within you save for he foreskin (orlah), remove it and eliminate your blemish – “Walk before Me and be perfect.” [this verse].’” Similarly, we read (Bereshis Rabbah 11:6), “Everything that came into being during the six days of Creation requires improvement – for example, the mustard see needs to be sweetened…even man needs rectification.”  … [Footnote of Rav Yisrael (Salanter):] this idea clarifies the Midrash (Bereshis Rabbah 30:10): “The verse states, ‘Noach walked with God’ (Genesis 6:9).   Rav Yehudah said: This may be likened to a king who had two sons – one an adult and the other a child. To the child he said, “Walk with me,’ but to the adult he said, ‘Come and walk before me.’ Similarly, to Avraham, whose strength was great, [He said] ‘Walk before Me and be perfect’ [this verse]. However, to Noach, whose strength was weak, [the Torah says,] ‘Noach walked with God.’”   Since Noach (according to his level) was not commanded concerning bris milah, he did not have the ability to achieve true rectification.   Rather, the level he reached, with the help of Heaven, was that of subduing his evil inclination. As Chazal state Sukkah 52b: “A person’s [evil] inclination intensifies itself over him every day, and if not for the help of KaKadosh Baruch Hu, man would not be able to overcome it” (see the text). This is the meaning of the verse: “Noach walked with God.” On the other hand, after Avraham removed his blemish (his foreskin), all the forces of his personality were rectified. Therefore, he was able to proceed on his own, to observe the way of Hashem “with heartfelt gladness, like one who walks with a flute” Isaiah 30:29. This is the meaning of the verse, “Walk before Me.”   OHRYIS 308-9