The following account shows the indelible mark that God's Messenger has imprinted on people of every age:
One of Ibn Sina's students told Ibn Sina that his extraordinary understanding and intelligence would cause people to gather around him if he claimed prophethood. Ibn Sina said nothing. When they were travelling together during winter, Ibn Sina woke up one morning at dawn, woke his student, and asked him to fetch some water because he was thirsty. The student procrastinated and made excuses. However much Ibn Sina persisted, the student would not leave his warm bed. At that moment, the cry of the muezzin (caller to prayer) called out from the minaret: "God is the greatest. I bear witness that Muhammad is the Messenger of God."
Ibn Sina considered this a good opportunity to answer his student, so he said:
You, who averred that people would believe in me if I claimed to be a prophet, look now and see how the command I just gave you, who have been my student for years and have benefited from my lessons, has not had the effect of making you leave your warm bed to fetch me some water. But this muezzin strictly obeys the 400-year-old command of the Prophet. He got up from his warm bed, as he does every morning together with hundreds of thousands of others, climbed up to this great height, and bore witness to God's Unity and His Prophet. Look and see how great the difference is!
The Prophet's name has been pronounced five times a day together with that of God for 1,400 years all over the world.