\documentclass{book}
\usepackage{amsthm,amssymb,amsmath}
\usepackage{graphicx,caption,subcaption}
\usepackage{hyperref}[2010/09/11]
\newtheorem{definition}{تعریف}[section]
\newtheorem{theorem}{قضیه}[section]
\newtheorem{lemma}{لم}[section]
\newtheorem{proposition}{گزاره}[section]
\newtheorem{corollary}{نتیجه}[section]
\newtheorem{remark}{ملاحظه}[section]
\usepackage[localise]{xepersian}
\settextfont{XB Zar}
\setdigitfont{Persian Modern}

\begin{document}

\begin{equation}
\begin{split}
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
& f=ma \\
\end{split}
\end{equation}
\end{document}