\documentclass[11pt]{article}
\usepackage{empheq}

\usepackage{xepersian}
\newcommand*\widefbox[1]{\fbox{\hspace{2em}#1\hspace{2em}}}

\begin{document}
\begin{empheq}[box=\widefbox]{equation}
  \bar{\nabla}^{\mu} \bar{h}_{\mu\nu} = 0
\end{empheq}

\begin{subequations}
\begin{empheq}[box=\widefbox]{align}
  \bar{\nabla}^{\mu} \bar{h}_{\mu\nu} & = 0 \\
  \bar{\nabla}^{\mu} \bar{h}_{\mu\nu} & = 0
\end{empheq}
\end{subequations}
\end{document}