NUM252 It is a grave sin to speak against the Jewish people as a whole. The Midrash states that whoever serves as a leader of the Jewish people must be very careful how he addresses them. According to one opinion because Moshe said, "Hear now you rebels," he was told," therefore you shall not bring the assembly into the land which I have given them" (verse 12). Yeshayahu said to God, "I am a man of unclean lips, and I dwell in the midst of the people of unclean lips" (Yeshayahu 6:5). For this statement he was severely punished. Eliyahu said to God, "I have been very zealous for the Lord God of hosts; for the children of Israel have forsaken your covenant" (I Melochim 18:10). He was severely punished for his statement. (Yalkut Shimoni 764).