Hi Ahmed,
welcome to the forum!
If anything doesn't work, save it in a box.

That's good for TikZ nodes, but also for tabular content or content that shows issues within another environment.
Declare a box:
Use it, in this case we chose the array package to define a new column type, here C for right to left centered:
Code: Select all
\usepackage{array}
\newcolumntype{C}{>{\begin{lrbox}{\mybox}}c<{\end{lrbox}\AR{\unhbox\mybox}}}
Then you can use C in your table instead:
Complete example:
Code: Select all
\documentclass[14pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[LAE]{fontenc}
\usepackage[german,arabic]{babel}
\newsavebox{\mybox}
\usepackage{array}
\newcolumntype{C}{>{\begin{lrbox}{\mybox}}c<{\end{lrbox}\AR{\unhbox\mybox}}}
\begin{document}
محمد - أحمد
\begin{tabular}[]{|C|C|}\hline
محمد & أحمد
\\\hline
\end{tabular}
\end{document}
That's similar to what Salim Bou suggested.
Stefan