\documentclass[12pt,twoside]{book}
\usepackage{xepersian}
\settextfont{XB Zar}%Adobe Arabic}%XB Kayhan}
\setlatintextfont{Times New Roman}%Adobe Arabic}%XB Kayhan}
\setdigitfont{XB Zar}
\usepackage[all]{xy}


%-----------------------------------------------------------------------------
\begin{document} 

\entrymodifiers={=<1.3pc>[o][F-]}

\xymatrix{
A \ar[dr]_{f;g} \ar[r]^{f} & B \ar[d]^{g} \ar[dr]^{g;h}  \\
& C \ar[r]_{h}& D
}

\end{document}