John Gill Commentary Job 41:12

"I will not keep silence concerning his limbs, Nor his mighty strength, nor his goodly frame." — Job 41:12 (ASV)

I will not conceal his parts
The parts of the leviathan; or "his bars", the members of his body, which are like bars of iron:

nor his power;
which is very great, whether of the crocodile or the whale:

nor his comely proportion;
the symmetry of his body, and the members of it; which, though large, every part is in just proportion to each other.