This is a day when they shall not be able to speak
That is the day they do not spea
This is the Day they shall not speak
This is the day on which they speak not
That (is) a day/time they do not speak
On the Day of Judgment, the disbelievers will loose their ability to talk
This is a day in which they will not be able to speak
This is a day when they shall not be able to speak
This is a Day (on which) they will not be able to speak too
This is a day when they shall not be able to speak
That will be a Day when they shall not speak (during some part of it)