\documentclass[a4paper,11pt]{book}
\usepackage{amsmath}
\usepackage{multido,xcolor}
\usepackage[colorlinks]{hyperref} 

\usepackage{xepersian}
\settextfont[Scale=1]{Yas} 
\setdigitfont[Scale=.9]{Yas} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\newcounter{mycounter}
\numberwithin{mycounter}{chapter}

\makeatletter

\newenvironment{example}
  {\par\noindent\examplehang\par\nobreak\noindent
   {\setRTL\hboxR{\refstepcounter{mycounter}\postdisplaypenalty=10000 %
   {\bfseries\upshape{\color{magenta}{\themycounter~~\bfseries{مثال}}}}\ \ignorespaces}}} %\examplename
  {\par\nobreak\noindent\examplehung\par\addvspace{\topsep}}

\newcommand{\examplehang}{% top 
  \begingroup%
    \setlength{\unitlength}{0.005\linewidth}% \linewidth/200
    \begin{picture}(0,0)(1.5,0)%
      \linethickness{0.8pt} \color{black}%
      \put(-3,2){\line(1,0){206}}% Top line
      \multido{\iA=2+-1,\iB=50+-10}{5}{% Top hangs
        \color{black!\iB}%
      }%
    \end{picture}%
  \endgroup%
}%

\newcommand{\examplehung}{% bottom 
  \begingroup%
    \setlength{\unitlength}{.005\linewidth}% \linewidth/200
    \begin{picture}(0,0)(1.75,0)%
      \linethickness{2pt} \color{black}%
      \put(-3,0){\line(1,0){206}}% Bottom line
      \multido{\iA=0+1,\iB=50+-10}{5}{% Bottom hangs
        \color{black!\iB}%\iB
      }%
    \end{picture}%
  \endgroup%
}%

\makeatother

\begin{document}
\chapter{نام فصل}
\section{بخش اول} 
\section{بخش دوم} 
\section{بخش سوم}
\begin{example} \label{1} 
این یک مثال است.  
\ref{1}
\end{example} 
\begin{example}  \label{2}
ارجاع به مثال دوم 
\ref{2}

\end{example} 

\end{document}