Al Fadi talks about the challenge that a muslim posted  on October 11 that the doctrine of the trinity is unbiblical.  Al Fadi explains that though the word trinity is not found in the Bible,but the concept is found all over the old and the new testaments.  He counter the challenge by another post on October 14 that  says :"prove to us that the word "Ahad" means one from the  Quran".  You can go to Cirainternational u tube for more details.