The verse in Bereishis 49:19 states:
גָּ֖ד גְּד֣וּד יְגוּדֶ֑נּוּ וְה֖וּא יָגֻ֥ד עָקֵֽב
Is is the Chabad Minhag to read this verse, followed by the reverse of it, as part of Krias Shema She'al HaMita.
What is the source for reading it backwards and what is the intended meaning?