She must hold fast, or they would not be able to.

"You hold fast to the one, and I will do the same by the other."

I tried to push her away, but she held fast.

She held fast to his hand as he tried to pull away.

She tried other doors, and even a window, but found them all held fast.

But the 72 employees who walked on Day 1 out have held fast.

I could feel his eyes burning into my back, but he held fast.

To do what she asked, he must hold fast all the way to his soul.

If I held fast, however, the water level would fall when the storm passed.

And so, too, must he hold fast to his purpose.