Midrash for Numbers 1:6

To Shimon, Shelumiel ben Tzurishaddai. Even though his descendant is Zimri, on whose account 24,000 died in a plague, G-d made peace with him and placed him next to Reuben, who had done repentance (a ba'al t'shuvah). Therefore it is said, "ben tzuri-shaddai," ("Shaddai is my rock")...