Midrash for Numbers 25:9

"When a person incurs guilt accidentally by [transgressing one among] all of the commandments of YHVH": This is that of which the Bible says: "And indeed I have witnessed under the sun the place of judgment..." (Ecclesiastes 3:16). Rabbi Eliezer and Rabbi Joshua [in conversation]...

R. Nachman said in the name of Rab: "What is the meaning of the passage (Prov. 18, 23) The poor speaketh entreatingly, but the rich answereth roughly. The poor speaketh, refers to Moses; and the rich, etc., refers to Joshua." What is the reason [for such an interpretation]? Shall I say because it is written (Josh. 6, 21) And he laid them out before the Lord? And R. Nachman explained this that he laid them down closely upon one another [and pleaded with Him], etc. Did not Pinchas do the same? As it is written (Ps. 106, 30) Then stood up Pinchas, etc. It ought to be written, va-yithpalel, which means, and he prayed, instead of va-ye phalel (debated). R. Elazar said: "Infer from this that he had debated with his Creator. He cast them before the Lord, saying: 'Sovereign of the Universe! were these so worthy that on account of them twenty-four thousand persons of Israel should fall? — as it is written (Num. 25, 9) And those that died in the plague were twenty and four thousand.'" And if you infer it from the passage (Josh. 7, 7) Wherefore hast Thou caused this people to pass over the Jordan?— did not Moses say similar to this (Ex. 5, 22) Wherefore hast thou let so much evil come upon this people? We must therefore say, because Joshua said (Jos. 7, 7) Would that we had been content, and dwelt on the other side of the Jordan. (Ib., ib. 10) And the Lord said unto Joshua: Get thee up. R. Shilla lectured: The Holy One, praised be He! said to him: "Thine [transgressions] is worse than theirs, for I have said (Deut. 27, 4) And it shall be as soon as ye are gone above the Jordan, that ye shall set up these stones, but ye went a distance of sixty miles before ye did this." After Shilla went away, Rab appointed an interpreter and lectured (Jos. 11. 15) As the Lord commanded Moses His servant, so did Moses command Joshua; and so did Joshua; he left nothing undone of all that the Lord commanded Moses. But why is it written, Get thee up? It means that the Lord said to him: Thou thyself hast caused all the evils, [because thou didst declare as accursed the goods of Jericho]. And this is meant by the passage (Ib. 8, 2) Only its spoil and its cattle shall ye take for booty unto yourselves.

Another explanation. They sinned at Shittim, they were smitten at Shittim, and they were healed by means of Shittim. They sinned at Shittim; as it is said: And Israel abode in Shittim (Num. 25:4); they were smitten at Shittim, as it is said: And those that died by the plague (ibid., v. 9); and they were healed by means of Shittim, as it is said: Boards of acacia (shittim) wood. You find that they did not leave that place until Phinehas arose and turned away His wrath, as it is said: Phinehas the son of Eleazar, the son of Aaron the priest, hath turned My wrath away from the children of Israel (ibid., v. 11). The Holy One, blessed be He, declared: In the world-to-come I will heal at Shittim, as it is said: And it shall come to pass in that day, that the mountains shall drop down sweet wine, and the hills shall flow with milk, and all the brooks of Judah shall flow with waters, and a fountain shall come forth of the house of the Lord, and shall water the valley of Shittim (Joel 4:18).