Allah (SWT ) says in Surah Al Baqarah Verse 3 about the pious
believers that they are those: Who believe in the Ghaib (the unseen) , And establish prayers and spend out of what we have provided for them”.
The faith of the believer does not contain doubts because doubts
vanish where faith exists.
There is no real success in life without true faith, and true faith can never exist with doubt.