This is an example to illustrate my point:

Any help will be greatly appreciated.
Thanks in advance.
Code: Select all
\documentclass{article}
\usepackage{framed}
\begin{document}
\begin{leftbar}
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text \begin{equation}
a=b
\end{equation}
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
\end{leftbar}
\end{document}