Albert Barnes Commentary Job 39:3

"They bow themselves, they bring forth their young, They cast out their pains." — Job 39:3 (ASV)

They bow themselves - literally, they curve or bend themselves; that is, they draw their limbs together.

They cast out their sorrows - That is, they cast forth the offspring of their pains, or the young which cause their pains. The idea seems to be that they do this without any of the care and attention which shepherds are obliged to show to their flocks at such seasons. They do it when God alone guards them; when they are in the wilderness or on the rocks far away from human dwellings. The leading thought in all this seems to be that the tender care of God was over his creatures, in the most perilous and delicate state, and that all this was exercised where people had no access to them, and could not even observe them.