I bet you can't find any quote/footage etc of Blair saying that. I think he said something along the lines of he prayed he was making the right decision and has subsequently stated that his God will be his ultimate judge but he never said that God told him to invade. It's that sort of comment that creates hysteria amongst idiots!!!
Edit: Just seen that it refers to Bush, not Blair so apologies. I can well believe that Bush heard voices telling him to invade. It was probably his dad sneaking into his bedroom at night to whisper it in his ear!!