John Gill Commentary Job 40:7

"Gird up thy loins now like a man: I will demand of thee, and declare thou unto me." — Job 40:7 (ASV)

Gird up your loins now like a man: I will demand of you, and ,
declare you unto me
And prepare to give an answer to what should be demanded of him. The same way of speaking is used in (Job 38:3) ; (See Gill on Job 38:3).