This post has been removed; it's not a history question but simply an English usage question - particularly since this usage could still be used today, as in: pray x-post this question to /r/asklinguistics or the /r/Linguistics stickied Q&A post.

In this context, 'pray' works like 'please', but means roughly 'I pray that you would ...'. See this dictionary definition under adv http://www.thefreedictionary.com/pray