Word by Word Analysis

فَلَمَّا ذَهَبُوا۟ بِهِۦ وَأَجْمَعُوٓا۟ أَن يَجْعَلُوهُ فِى غَيَـٰبَتِ ٱلْجُبِّ ۚ وَأَوْحَيْنَآ إِلَيْهِ لَتُنَبِّئَنَّهُم بِأَمْرِهِمْ هَـٰذَا وَهُمْ لَا يَشْعُرُونَ 15

So when they took him [out] and agreed to put him into the bottom of the well... But We inspired to him, "You will surely inform them [someday] about this affair of theirs while they do not perceive [your identity]."