“So-and-so has a hand in this,” and “I have a hand in this,” meaning that one is capable of it. To say that his ability is complete, however, requires wording that conveys this. They also say, “So-and-so has no hand in it,” meaning that he has neither the strength nor the capacity for it. As the poet said:

I promised the diviner of al-Yamāmah whatever fee he chose,
and the diviner of Hajr likewise, if they cured me.
Every incantation they knew, every soothing draught,
they gave me to drink.
They said, “May Allah heal you! By Allah, we have no power
over what your ribs enclose.”