4:135: “O you who believe, stand firm for justice as witnesses for Allah, even against yourselves.” Thus, a person’s testimony against himself is his admission against himself.
In the authentic hadith recounting the story of Mā‘iz: “When he had testified against himself four times, the Messenger of Allah, may Allah bless him and grant him peace, had him stoned.”
Allah Most High says:
7:37: “They said, ‘We testify against ourselves.’ The life of this world deceived them, and they testified against themselves that they had been disbelievers.”
These and many more examples show that, for a witness’s testimony to be accepted before a judge or anyone else, he need not use an explicit formula of testimony. This is the position of Mālik and the people of Medina, and the apparent meaning of Ahmad’s words. None of the Companions or Successors is known to have stipulated this requirement.
Ibn ‘Abbās said: “Trustworthy men testified before me—the most trustworthy of them in my estimation being ‘Umar—that the Messenger of Allah, may Allah bless him and grant him peace, forbade prayer after the dawn prayer until sunrise, and after the afternoon prayer until sunset.”
It is well known that they did not use an explicit formula of testimony. Likewise, when the Messenger of Allah, may Allah bless him and grant him peace, testified that the ten would be in Paradise, he did not use an explicit formula of testimony. Rather, he said: “Abū Bakr is in Paradise, ‘Umar is in Paradise, ‘Uthmān is in Paradise, and ‘Alī is in Paradise”—the hadith continues.
Muslims unanimously agree that when a disbeliever says, “There is no god but Allah; Muhammad is the Messenger of Allah,” he has entered Islam and borne true testimony. His entry into Islam does not depend on using an explicit formula of testimony. He is included in the Prophet’s words, may Allah bless him and grant him peace: “Until they testify that there is no god but Allah.” In another wording: “Until they say, ‘There is no god but Allah.’” «1»
This shows that their saying, “There is no god but Allah,” constitutes testimony on their part. The supporting examples in the Quran and Sunnah are too numerous to list. Those who stipulate an explicit formula of testimony therefore have no evidence on which to rely. And Allah knows best.
As for the level of making things known and conveying information, it takes two forms: through words and through actions.