The same applies to arithmetical propositions: knowledge of products, ratios, sums, and the like is necessary knowledge for one who knows them. If a group whose reports constitute mass transmission informs someone of these things, he acquires knowledge of them, even though they are reporting only what they know by necessary knowledge.

Likewise, the truthfulness of a truthful person and the lying of a liar are known by necessity to those who have dealt with them and put them to the test. Those to whom this information reaches through mass transmission know it through reports.

For this reason, the knowledge that Muhammad, may Allah bless him and grant him peace, was truthful, known for his truthfulness, and did not lie has reached those who never dealt with him through mass transmission. Those who had put him to the test, whether his enemies or others, agreed that he was truthful and trustworthy. Thus, when Heraclius questioned Abū Sufyān—who was then among the fiercest enemies of the Messenger of Allah, may Allah bless him and grant him peace—he asked:

“Did you ever accuse him of lying before he said what he has said?”

Abū Sufyān replied, “No.”

He thus stated that neither he nor the other Quraysh had accused him of lying, let alone reported that he had lied. Indeed, they used to call him “the Trustworthy.”

Abū Sufyān gave this account in the presence of a group of his people who affirmed what he said, despite having every reason to contradict him had he lied. Heraclius therefore learned from this that Muhammad did not lie. He said:

“I knew that he would not refrain from lying about people only to go and lie about Allah.”

This and similar cases form a broad subject. Thus, knowledge of what reports convey is attained when the informant possesses necessary knowledge, whether or not he is an eyewitness.