How does one increase certainty in God, and does high certainty lead to miracles or abandoning the taking of means, and how can a person know that their certainty is great?

Certainty increases by frequently contemplating the Book of Allah, pondering its meanings and cosmic signs, and the meanings of Allah Almighty’s attributes, and by frequently asking Allah Almighty for faith, certainty, and guidance. This includes the supplication: "O Allah, apportion to us of Your awe that which will interpose between us and Your disobedience, and of certainty that which will make the calamities of the world easy for us." It also increases by the servant acting upon what he knows of the religion, worshipping Allah, remembering Him in every state, and frequently looking into the texts of revelation that include encouragement and deterrence, and promise and warning. The increase in certainty does not necessitate the existence of miracles or abandoning means, for the Prophets and Companions used to earn a living and work.