What did Allah prepare for those among the Jews and Christians who believe ?

(57 : 28)
O you who believe (in Musa (moses) (i.e. Jews) and Isa (Jesus) (i.e.
Christians)! Fear Allah, and believe in His Messenger (Muhammad (PBUH) ),
He will give you a double portion of His Mercy, and He will give you a
light by which you shall walk (straight). And He will forgive you. And
Allah is Oft-Forgiving, Most Merciful.