﴿ ٱلَّذِينَ يَجْعَلُونَ مَعَ ٱللَّهِ إِلَٰهًا ءَاخَرَ ۚ فَسَوْفَ يَعْلَمُونَ ﴾

“who assert that there are, side by side with God, other divine powers as well: for in time they will come to know [the truth].”

those mockers who set up besides God another god this entire clause is an adjectival qualification; but it is also said to be the subject and because there is an implicit conditional meaning in the above-mentioned clause the particle fā’ has been inserted into the predicate which is the following soon they will know the sequel of their affair.