"without cause" (chinnam) is a PIERCING REBUKE of [hasatan]!
This verse must be read in context. When the LORD had stated His judgement of Job, that Job was blameless and upright, who fears God & turns away from evil, [hasatan] had said the LORD's judgement was wrong! Stated in less diplomatic terms [hasatan] told God that He did not understand Job (or man.) Job was a mercenary servant (like all men at best) who would curse God to His Face if God were to remove the hedge about him & everything he has. God then allowed [hasatan] to prove [his] contradiction.
The contradiction proved SPECTACULARLY wrong. Job did not curse God to His Face as [hasatan] had unequivocally stated, in front of the whole heavenly assembly, Job would do. This was SPECTACULAR failure done by a very proud spirit who felt [he] could contradict God to His Face before the whole heavenly assembly.
As a result of [hasatan's] contradiction being a spectacular failure the LORD pronounced, before the whole heavenly assembly, a piercing rebuke of [hasatan] by stating that [hasatan's] now obviously wrong contradiction had moved the LORD to destroy/ruin/afflict Job without cause! (A lot of people were killed, all of Job's children & many of Job's servants. This was no small matter but very very serious.)
To what can this be compared to? Imagine one the brightest mathematicians of the age going before the god of mathematicians, someone acknowledged as having no equal in mathematics, and contradicting the god of mathematicians saying the god of mathematicians was wrong & he could prove it. As the brightest mathematicians presents his proof, it only proves itself to be spectacularly wrong. Then the god of mathematicians pronounces, in front of an enormously large group of mathematicians, that the contradiction was wrong! Maybe to those of us who make mathematical mistakes all the time, any judgement of error on our part is just water on a duck's back, but to the brightest of mathematicians who put [perfection] above all, this recognition, judgement, & highlighting of his error is a piercing rebuke!*