What is the intention for fasting the obligatory fast of the month of Ramadan, for performance (adaa’) and not for making up (qadaa’), and should it be by saying to oneself silently, “I will fast tomorrow, performance of the obligatory fast of the month of Ramadan,” without moving the lips or tongue, or how should it be, and is there a concise wording for the intention?

Intention (niyyah (definition)) is an act of the heart and does not require verbalization; in fact, verbalizing it is an innovation (bid‘ah). It is sufficient for a person to intend fasting in their heart during any part of the night. Sheikh al-Islam Ibn Taymiyyah mentioned that the intention for fasting in Ramadan (definition) does not necessitate verbalization, by the consensus of the imams; rather, the intention of the heart is sufficient.