What are the obligatory and recommended matters concerning sincerity and intentions, and is it necessary to perform heartfelt actions before prayer, ablution, and ritual bathing?

Sincerity in worship is a religious obligation, and it is an act of the heart related to intention, with no involvement of the tongue. If you are sincere to your Lord with your heart when intending to pray, this is the sincerity required by Islamic law. Anything beyond that is a whisper from Satan (waswas) that must be avoided. There is no need for you to say to yourself, "Pray, for Allah knows your intention"; this is a given and only increases the whispers. Moreover, it is not prescribed, as uttering the intention aloud is an innovation (bid'ah). It has not been reported that the Prophet (peace be upon him) or any of the Pious Predecessors ever vocalized the intention for an act of worship. Intention naturally occurs with the knowledge of the action, and speaking it aloud is a form of obsession.

The obligatory acts of the heart before worship are sincerity, intending to draw closer to Allah, and purifying the heart from ostentation. One should confine oneself to the intention and sincerity in the heart and refrain from vocalizing any superfluous phrases.