﴿ مِّن وَرَآئِهِۦ جَهَنَّمُ وَيُسْقَىٰ مِن مَّآءٍۢ صَدِيدٍۢ ﴾

“with hell awaiting him; and he shall be made to drink of the water of most bitter distress,”

beyond him that is in front of him is Hell which he will enter and he is given to drink in it of festering fluid — which is what issues out of the insides of the people of the Fire mixed with pus and blood —