Берешит 9:9 Комментарий: Rashi, Chizkuni, Sforno & Kitzur Ba'al HaTurim

ואני הנני AND I BEHOLD I — “I am in agreement with you”; He said this because Noah feared to fulfil the duty of propagating the species until the Holy One, blessed be He, promised him that he would not again destroy the world and this promise God made (Midrash Tanchuma, Noach 11). Ultimately He said to him, “If you are still anxious I am willing to give to My promise the permanence and strength of a covenant and I will give you a sign.”

ואני הנני, “and as far as I am concerned, etc;” according to Rashi, this is G-d’s way of saying that He agreed with Noach who had not wanted to resume normal marital relations until specifically encouraged by G-d to do so. He waited for G-d’s promise not ever again to bring on the kind of destruction of the human race that he had just been a witness to.

ואני הנני מקים את בריתי, this promise is conditional on man keeping his part of the bargain, bringing murderers to justice. If, however, innocent blood will be shed in the manner it had been before the deluge, this may lead to destruction of the earth (not necessarily by water). This is what is meant in Numbers 35,33 הדם הוא יחניף את הארץ ולארץ לא יכופר לדם אשר שפך בה כי אם בדם שפכו “for blood turns the earth into a hypocrite and there will be no atonement for the land except through the blood of him who has spilled it.”