Al-Humaza • EN-AL-JALALAYN
﴿ فِى عَمَدٍۢ مُّمَدَّدَةٍۭ ﴾
“in endless columns!”
in outstretched mumaddadatin is an adjective qualifying the preceding noun ‘amadin columns read ‘umudin or ‘amadin and will therefore be inside the columns.