Share 'Making a Post "Sticky" in Tumblr'

Hi all... I'm wondering if anyone knows how I can make a single post stay as number one on my tumblr page as I add new content? My tumblr page is an art portfolio and I would like my "welcome" post to stay first as I add new content without having to continually change the dating of posts and thus to stay true to the medium of blogging. any help would be appreciated