Albert Barnes Commentary Jeremiah 6:15

"Were they ashamed when they had committed abomination? nay, they were not at all ashamed, neither could they blush: therefore they shall fall among them that fall; at the time that I visit them they shall be cast down, saith Jehovah." — Jeremiah 6:15 (ASV)

They are brought to shame because
They have committed abomination:
Shame nevertheless they feel not;
To blush nevertheless they know not;
Therefore they shall fall among the falling;
At the time when I visit them, they shall stumble,
Saith Yahweh.

The fact is expressed that their conduct was a disgrace to them, though they did not feel it as such. Abomination has its usual meaning of idolatry (Jeremiah 4:1).