Albert Barnes Commentary Job 16:12

"I was at ease, and he brake me asunder; Yea, he hath taken me by the neck, and dashed me to pieces: He hath also set me up for his mark." — Job 16:12 (ASV)

I was at ease - I was in a state of happiness and security. The word used here (שׁלו shâlêv) means sometimes to be “at ease” in an improper sense; that is, to be in a state of “carnal security,” or living unconcerned in sin (Ezekiel 23:42); but here it is used in the sense of comfort. He had everything desirable around him.

But he hath broken me asunder - He has crushed me.

He hath also taken me by my neck - Perhaps as an animal does his prey. We have all seen dogs seize upon their prey in this manner.

And set me up for his mark - Changing the figure, and saying that God had directed his arrows against him; so Jeremiah (Lamentations 3:12):

He hath bent his bow,
And set me as a mark for the arrow.