Midrash su I Re 20:8

When the king of Israel heard these words, he said: This matter does not concern me alone. The elders must make the decision. Thereupon, the king of Israel assembled all the elders of the land and said: “Mark, I pray you, and see how this man seeketh mischief; for he sent unto me for my wives, and for my children, and for my silver, and for my gold; and I denied him not.” And all the elders and all the people said unto him: “Hearken thou not, neither consent” (I Kings 20:8). He followed the advice of the elders, and the king of Israel went out, and smote the horses and chariots, and slew the Arameans with a great slaughter (ibid., v. 21). Therefore, one must always consult with elders. And thus it is written: Moses … and Aaron and his sons, and the elders of Israel (Lev. 9:1).