﴿ وَمَآ أَدْرَىٰكَ مَا ٱلْعَقَبَةُ ﴾

“And what could make thee conceive what it is, that steep uphill road?”

And what will show you what will make known to you what the obstacle is? that he is to surmount — intended to emphasise its enormity this statement is a parenthetical one. He explains the way to surmount it by saying