﴿ فَذَٰلِكَ يَوْمَئِذٍۢ يَوْمٌ عَسِيرٌ ﴾

“that very Day shall be a day of anguish,”

that day that is to say the time of the sounding yawma’idhin is a substitution for the preceding subject and is not declined because it is annexed to something that cannot be declined; the predicate of the subject is the following will be a harsh day idhā is operated by what is indicated by the statement ishtadda’l-amru ‘for when the trumpet is sounded the situation will be terrible’