\documentclass[10pt,a4paper]{article}
    \usepackage{amsmath} 
    \usepackage[subnum]{cases}
   \usepackage{xepersian}
    \begin{document}
    \begin{numcases}{}
     (H-\lambda I)x=x^(k)=kx^{(k-1)}+ p^(k)(\lambda)e_1 ,&  $k=0,1,2,\ldots$ \label{eq:sam1}
    \\
    y^(k)(H-\lambda I)=ky^{(k-1)H}+ p^(k)(\lambda)e_n^T, &  $k=0,1,2,\ldots$ \label{eq:sam2}
    \end{numcases}
    با توجه به معادله~%
    \ref{eq:sam1}
    \end{document}