The phrase “at that time ” evidently refers to the event that Jesus had just mentioned, namely, the ‘ pitching of the weeds into the fiery furnace. ’
وَيَحْدُثُ هٰذَا خِلَالَ ٱلْجُزْءِ ٱلْأَخِيرِ مِنَ ٱلضِّيقِ ٱلْعَظِيمِ .‏