The foundation of recitation is that it involves using the tools of vocalization, including the throat, tongue, lips, and other components of the vocal apparatus. Furthermore, there must be a minimum level of audibility in recitation, such that an individual can hear themselves. Anything less than that is considered self-speech and is not considered for legal rulings. As Allah, the Almighty, says: “Do not move your tongue with it to hasten it. It is for Us to collect it and [to make it] recitation.” (Al-Qiyamah 75:16-17)
Based on this, someone who prays and does not utilize the components of the vocal apparatus, and does not move their tongue when it is required, is like someone who has not recited.
In general, recitation is one of the six pillars of prayer in our school of law, and prayer is not valid without it.
And Allah knows best.
Fatwa by Dr. Khālid Naṣr