\documentclass{article} 
\usepackage{xepersian}
\setdigitfont{XB Zar}
\begin{document}
\begin{center} 
$3\not |\gamma$.\\ 
$3\ \ \not | \ \ x\gammay$.\\
$3\quad \not| \quad \gamma$.\\
\end{center}
\end{document}