Midrash su Numeri 25:1

And Jacob sat in the land (Gen. 37:1). Whenever Scripture uses the expression and he sat (also translated “and he dwelt”), it connotes misfortune: And Israel sat in the land of Egypt, in the land of Goshen, … and the time drew near that Israel must die (Gen. 47:29); And the people sat down to eat and drink, and rose up to make merry (Exod. 32:37); And there fell of the people on that day three thousand men (Exod. 38:28); And they sat down to eat bread; and they lifted up their eyes and looked, and, behold, a caravan of Ishmaelites (Gen. 37:25); And Judah and Israel sat safely (I Kings 5:5); And the Lord raised up an adversary against Solomon (ibid. 11:14); And Israel sat among the cedars, etc., and the people began to commit harlotry (Num. 25:1). You may explain every other use of “and he sat” with this negative implication. In this instance And Jacob sat is followed by and Joseph brought evil report of them unto his father (Gen. 37:2).

"in the plain": We are hereby taught that he rebuked them for what they did in the plains of Moav, viz. (Bamidbar 25:1)

At that time the Lord said unto Moses: Behold, the days are approaching for thee to die. Take ‎thou Joshua, the son of Nun, thy servant, and place him in the tabernacle that I may give him ‎my commandments, and Moses did so.‎‏ ‏And the Lord appeared in the tabernacle in a pillar of ‎cloud, and the pillar of cloud stood at the door of the tabernacle, and the Lord commanded ‎Joshua, the sun of Nun, saying unto him: Be thou strong and courageous for thou shalt bring ‎the children of Israel to the land which I have given unto them, and I will be with thee.‎‏ ‏And ‎Moses said unto Joshua: Be strong and courageous, for thou wilt cause the children of Israel to ‎inherit the land, and the Lord will be with thee, He will not leave thee nor forsake thee. Fear ‎not and be not dismayed.‎‏ ‏And Moses called to all Israel and he said unto them: Ye have seen ‎all the good which the Lord your God hath done for you in the wilderness. Now therefore ‎observe ye all the words of this law and walk in the way of the Lord your God, do not turn from ‎the path which the Lord hath commanded you, neither to the right nor to the left. And Moses ‎taught the child ren of Israel statutes, and judgments, and laws, to practice them in the land, ‎as the Lord had commanded him, behold they are written in the book of the law of God which ‎he gave unto the children of Israel by the hand of Moses. And when Moses had finished ‎instruct ing the children of Israel, the Lord said unto him: Go up to Mount Abarim and die ‎there, and thou shalt be gathered to thy people like unto Aaron, thy brother. And Moses went ‎up, as the Lord had commanded unto him, and he died there, in the land of Moab, in the ‎fortieth year of the children of Israel’s departure from the land of Egypt. And the children of ‎Israel wept for Moses in the plains of Moab, thirty days; so the days of mourning for Moses ‎were ended.‎