MWhat is the meaning of "stand by" in the chapter IV of The Great Gatsby​ by F. Scott Fitzgerald

I'd like to know the precise meaning of "stand by" in the following passage from the chapter IV of The Great Gatsby​ by F. Scott Fitzgerald, knowing that "retribution" means punishment:

“I’ll tell you God’s truth.” His right hand suddenly ordered divine retribution to stand by.

Does he raise his hand to delay or to communicate a sense of waiting to divine retribution? Or else, does it mean to be available and ready to act if needed or called upon? is it a little like saying "May God strike me dead if I lie"?

Thank you.