documentclass[border=5mm]{standalone}
usepackage{tikz}
usetikzlibrary{decorations.text}
usepackage{fontspec}
usepackage[rldocument]{bidi}

setmainfont[Script=Arabic]{Amiri}

tikzset{decoration={text along path,
text={Very very long text I need to show it from right to left}}}

begin{document}

begin{tikzpicture}
    path [decorate] (0,0)..controls +(45:4cm) and +(225:4cm)..(8,0);
end{tikzpicture}

end{document}

left to right from it show to need I text long very Very