The Ruling on Uttering the Intention with the Tongue
What is the ruling on uttering the intention with the tongue when beginning the prayer, or does its seat in the heart suffice?
The seat of the intention is the heart, and uttering it with the tongue is recommended, so that the heart's resolve is joined to the tongue's act, and to keep intrusive thoughts at bay.
The seat of the intention is the heart, and uttering it is contrary to what is preferable, since it is not established from the Prophet ﷺ; it is recommended only for one afflicted with obsessive doubt, to drive that doubt away.
It is a sunnah to utter the intention quietly before the takbīr, so that the tongue assists the heart and the intention is present in all its parts at the opening takbīr.
The seat of the intention is the heart, and uttering it quietly is recommended so that the tongue agrees with the heart; saying it aloud is not prescribed in any case.