I'm searching for you...
http://showcase.netins.net/web/creative/lincoln/speeches/quotes.htm
from the site on Lincoln...
Abraham Lincoln On-line
http://showcase.netins.net/web/creative/lincoln/siteindex.htm
Well, this is an excellent source!
I made several searches using the phrase 'on God's side' with no success. Sorry. I also skimmed much of the text.
I did notice that you can have an on-line discussion with this Lincoln scholar.
Best of luck, and if you find it, please let me know.
I am guessing you are asking because you suspect the validity of the quote. My small research suggests you might be correct.
If you would like me to send you the text of the speeches I searched, please email me via Yahoo Answers. (it is a 55 page MS Word document)
This was an interesting question. Thanks
4 HOURS LATER...
see if this helps
This seems to be similar to the quote you included in your question...
Abraham Lincoln and religion
http://encyclopedia.thefreedictionary.com/Abraham+Lincoln+and+religion#endnote_rf-17
Abraham Lincoln's religious beliefs are a matter of controversy. As a youth, he was known among his friends as an admirer of the deist author Thomas Paine, and he wrote a manuscript challenging orthodox Christianity modelled on Paine's book The Age of Reason, which his friends burned to protect him from ridicule.[1] Raised by fundamentalist Baptists, Christianity was a force throughout his life. Lincoln read the Bible throughout his life, and quoted from it extensively. There is more disagreement about whether he experienced a conversion to Christianity later in life, particularly during his tenure as president. Several ministers have claimed such conversions at various stages of Lincoln's life, with some of their statements contradicting those of the others.
When a pious minister told Lincoln he "hoped the Lord is on our side," the president responded, "I am not at all concerned about that.... But it is my constant anxiety and prayer that I and this nation should be on the Lord's side."[17]
17. ^ F.B. Carpenter, Six Months at the White House, p. 282. [10]
If you go to the website above, look up footnote 17 and click on the ‘10’ at the end of the line, it will take you to a library site with the complete text of the book, Six Months at the White House.