Ezra 9:1
Now when these things were done, the princes came to me, saying, The people of Israel, and the priests, and the Levites, have not separated themselves from the people of the lands, doing according to their abominations, even of the Canaanites, the Hittites, the Perizzites, the Jebusites, the Ammonites, the Moabites, the Egyptians, and the Amorites.
Soon after Ezra's return to Jerusalem, at a time when his brethren greatly needed the influence of his presence, the princes came to him. This was very soon after the returned exiles had offered sacrifices and delivered the king's commissions, when a few chief men brought a serious complaint.
The complaint was that the people of Israel, including the priests and the Levites, had not separated themselves from the peoples of the lands but were acting according to their abominations. The specific trespass was intermarriage with the surrounding heathen peoples, taking foreign daughters for themselves and for their sons, so that the consecrated people, the holy seed, mingled themselves with pagan nations. The princes and rulers themselves had been foremost in this trespass, their hand chief in it.
This was disobedience that disregarded God's holy commands given through Moses, losing sight of their holy character. By it Israel was joined to people whose worship and conduct opposed His ways. The disobedience was especially grievous because it came after God had punished them for earlier wrongdoing and yet granted them deliverance.