According to Palestinian negotiator Nabil Shaath, said by Bush to him, apparently in the same June 2003 meeting, as reported by BBC News http://news.bbc.co.uk/2/hi/americas/4317498.stm. Shaath later clarified this with "We understood that he was illustrating [in his comments] his strong faith and his belief that this is what God wanted." http://news.bbc.co.uk/2/hi/americas/4320586.stm, i.e. Shaath didn't take Bush's statement literally.
Denied by White House spokesperson Scott McClellan, October 6, 2005. Denied also by Mahmoud Abbas, who attended the meeting in question. Abbas said "This report is not true. I have never heard President Bush talking about religion as a reason behind the wars in Iraq and Afghanistan. President Bush has never mentioned that in front of me on any occasion and specifically not during my visit in 2003." http://www.smh.com.au/news/world/abbas-denies-bushs-mission-from-god-remark/2005/10/08/1128563027485.html.
Attributed, Disputed