\documentclass{book}
\usepackage{amsmath,amssymb,amsthm,amsfonts}
\usepackage[colorlinks=true]{hyperref}
\usepackage{xepersian}
\settextfont[Scale=1]{Yas}
\setlatintextfont[Scale=.95]{Times New Roman}
\setdigitfont[Scale=1]{Yas}
\defpersianfont\chapfont[Scale=3.3]{Yas}
\makeatletter
\def\theoremautorefname{قضیۀ}
\makeatother

\newtheoremstyle{Plain}% vahid
{\topsep}% measure of space to leave above the theorem. E.g.: 3pt
{\topsep}% measure of space to leave below the theorem. E.g.: 3pt
{\itshape}% name of font to use in the body of the theorem
{\parindent}% measure of space to indent
{\bf}%name of head font
{.}% punctuation between head and body
{0.5em}% space after theorem head; " " = normal interword space
{}%Manually specify head
\theoremstyle{Plain}
%\theoremstyle{definition}
\newtheorem{definition}{تعریف}[chapter]
\newtheorem{theorem}{قضیه}[chapter]
\newtheorem{Lemma}[theorem]{لم}
\begin{document}
\chapter{فضاهای متریک}
\begin{theorem}\label{theorem}
\end{theorem}

\begin{equation}
A\in G_{n}\stackrel{\text{\autoref{theorem}}}{\Longleftrightarrow}B\in G_{n}
\end{equation}
\end{document}