They would “learn ” from the features of that sign and“ know ” their true meaning. They would fully appreciate that “he is near at the doors. ”
وَسَيَعْرِفُونَ حَقَّ ٱلْمَعْرِفَةِ « أَنَّهُ قَرِيبٌ عَلَى ٱلْأَبْوَابِ » .‏