the_post_thumbnail() question

I want to remove the width and height from the coding in HTML for the_post_thumbnail();.

Output

<img width="250" height="219" src="https://localhost/websites/wordpress/wp-content/uploads/2015/02/8-best-cigars-gear-patrol-lead-full-v2-.jpg" class="attachment-post-thumbnail wp-post-image" alt="8-best-cigars-gear-patrol-lead-full-v2-">

I want to just control width/height with CSS. I can’t find a way to remove it though. Is there a way I can do this?