Is it permissible to verbalize the intention secretly in the heart, such as saying "I intend to perform ablution," or "I intend to perform ghusl," or "I intend to pray Asr"?

The intention (niyyah) is the purpose and its place is the heart. It is a condition for the validity of worship. Therefore, a Muslim must intend in their heart what they wish to do, such as removing ritual impurity with ablution (wudu) or performing a specific prayer. As for uttering the intention aloud with the tongue, there is a difference of opinion on this, and the preponderant view is that it is not prescribed.