Al-Adab Al-Mufrad #1288

Shahr ibn Hawshab said, "Me and my maternal aunt visited 'A'isha and said, 'Sometimes something occurs to one of us such that, if he had spoken about it, that would have been the end of his hopes for the Next World. If it were to be revealed, he would be killed for it.' She said the takbir three times and then said, 'The Messenger of Allah, may Allah bless him and grant him peace, was asked about that and said, "If that happens to one of you, he should say the takbir three times. Only a believer feels that.'"