[Zachariah] said, "My Lord, appoint for me a sign." A sign, [meaning] a mark. [Allah] said, "Your sign is that you will not speak to the people for three nights, sound (sawiyya)." That is: healthy, such that no illness prevents you from speaking. Qatada said: He was punished because he asked for a sign after the angels had addressed him directly and given him the glad tidings of John (Yahya), so his tongue was seized, and he became unable to articulate speech.