After leaving Morocco and before settling in Egypt, Maimonides visited Jerusalem and prayed at the site of the Holy Temple. Three days later, on 9 MarCheshvan, he visited Hebron and prayed at the Cave of Machpelah. Maimonides resolved to keep these two days—6 and 9 MarCheshvan—as a personal holiday (Charedim ch. 65 [5744 ed.).
Link: Rambam (Maimonides)
Noah was a tzadik, a very great man. He saved the entire world. But he didn't approach Abraham's greatness.
When G‑d told Noah to build an ark before the world would be destroyed, Noah built an ark.
But when G‑d told Abraham He was about to destroy the cities of Sodom and Gomorrah—cities corrupt and evil to the core—Abraham argued. He said, “Perhaps there are righteous people there! Will the Judge of All the Earth not do justice?”
Where Noah donned a warm coat for himself and his family, Abraham built a warm fire for the entire world.
Because Abraham felt a sense of ownership for the world in which he lived. If there was something wrong, it needed to be changed. Even if it had been decreed by the will of G‑d.