Use a rel= in features section

Hi there!

I’m hoping to call a rel in the text of my features section.
So, for example, in my features section I want the text “have a look at some of our work” to open a lightbox.

The code I am trying to use is:

<a href=”http:/” rel=”lightbox” data-lightbox-type=”iframe” />Have a look at some of our work</a>

However, when I enter it into the content section, Wordpress removes the “rel” code. How can I add this?