In context, it basically meant "Hopefully, magic will help you with your suicide mission." But where did it come from? Originally the line was "May the Force of others be with you," implying that the Force was some kind of communal pool of psychic mojo, like how body odor on a city bus combines into one dominant entity. The phrasing seems to reference our Earth religion of Catholicism, specifically the blessing Dominus vobiscum, which means "The Lord be with you." According to the film's producer, Gary Kurtz, that "comparison was exactly the intention."
These religious undertones didn't go unnoticed by the Christian community at the time, either. One of the first books ever written about Star Wars was a Christian-themed analysis, The Force Of Star Wars by Frank Allnutt. The book suggested that the message of the movie was about finding the Force (God) rather than spending your life "wallowing in the mud of pornography, dope, materialism and vain philosophies." Which brings up a new question: What the hell did Allnutt think was going on over at Tosche Station?
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