People of wisdom state:
Our Master the Prophet orders that one should speak to people according to their levels of understanding. As a matter of fact, when a Bedouin said to him, "Explain to me what Islam is. If I find it logical and reasonable, I will believe," our Master the Prophet replied, "This religion is based on two things: (1) to respect and to like all the commandments of Allahu ta'ala and (2) to feel pity for and to show mercy to all His creation."

Once upon a time, a man went to a city largely populated by Christians and stayed there for a while. Some time later, five or six people he had contact with came up to him. One of them was an atheist and the others were Christians. They said to him:

"We like you very much. We believe that your good moral qualities, sweet tongue, and smiling face come from your religion. Now give us information about Islam. We want to hear the Islamic religion from your lips. What is the Islamic religion?" He gave them the following answer:

"Islam is divided into two parts: faith [iman] and practice. Faith is to believe in Allah, angels, holy books, prophets, the life after death, and divine decree and preordainment. These principles exist in both Christianity and Judaism, though being different. We, for instance, cannot be Muslims if we do not believe in the prophethood of Musa 'alaihis-salam and 'Isa 'alaihis-salam."

"Why? They are not your prophets," they objected.

"All prophets are the prophets of Muslims as well because a person who does not believe that all prophets are the prophets of Allah cannot be a Muslim. If you, too, believe in all prophets including Muhammad 'alaihis-salam and the religion brought by him, all of you will become Muslims," he replied.

"How can it be? We eat pork," they asked.

"It is a matter pertaining to practice, and eating it is forbidden. The one who commits a forbidden deed does not go out of the fold of Islam," he clarified.

"In addition to it, we drink wine," they added.

"Similarly, it is a matter pertaining to practice, and drinking it is forbidden. There are also Muslims who consume alcoholic drinks. However, faith is different from practice. What matters is to have faith."

Thereupon, the atheist rushed forward excitedly and exclaimed:

"It has been understood. There is no need for you to explain it further."

"Yes, what I have told you is all about our religion," he said.

All of them were greatly surprised and looked at one another's faces. With this astonishment, they went out. However, the atheist came in again a bit later and stated:

"I am astonished by what you told us."

"Why are you astonished?" he asked.

"Our knowledge about Islam was quite different. Could you explain this religion to us again, please?"

After that man explained it once more, the atheist wrote down the Word of Testimony word by word and went out. Taking his friends along, he came to the presence of that man 10 or 15 minutes later and said, "I declare in public that I have become a Muslim." Then he recited, "Ash-hadu an laa ilaaha ill-Allah wa ash-hadu anna Muhammadan 'abduhoo wa rasooluhoo," thus taking a step toward eternal felicity.