Unit of Integral Domain divides all Elements

Theorem
Let $\left({D, +, \circ}\right)$ be an integral domain whose unity is $1_D$.

Let $\left({U_D, \circ}\right)$ be the group of units of $\left({D, +, \circ}\right)$.

Then:
 * $\forall x \in D: \forall u \in U_D: u \mathop \backslash x$

That is, every unit of $D$ is a divisor of every element of $D$.