Muslims believe that when a person dies two angels visit him in his grave. They question him about his Faith if he is found a believer his tomb is widened 70 cubits square and it is illumined. Then he is told to go to sleep like a bridegroom until the day of resurrection when Allah raises him up to reward him. But if he is found a "hypocrite" they order the tomb to squeeze him until his ribs are crushed. Based on this belief, people of Islam lead their life to get reward from Allah and they insist the principles given in the Koran.
Every people who adore their living in serving Allah, left an evidence of themselves in revealing the doubts in Allah. These kinds of evidence are piled as testimonials to the Islamic community. These testimonials serve in explaining the Almighty and his doctrine. And more over in olden days these testimonial serve to develop the generations towards Islamic. Thousand of testimonials serve today to reveal the truth in Islam and many famous people from good and sound inspirations on Islam and Allah have given their testimonials in serving God. Famous Muslims in those days have quoted their connection with the god and pointed out what makes the connection and preached them, to their off springs so that they may have their connections in servicing to God.
Leading a life of Koran every people in Islam had a close connection with Allah and they believe He has given and shown the way to lead a mortal life. Those who have found the signs and the offerings from Allah have voluntarily admitted themselves in relishing the Islamic community. They believe that serving the peoples of Islam is serving God. You can not state that all people can give their testimonial but for the true testimonials one has to lead and reveal what is faith? And who is the God? For such reasons you cannot have God in you, it is a state that your mind and soul get transformed towards god.